cs718 final term papers 2019|cs718 solved final term papers

cs718 final term papers 2019



#CS718 #CS718FinalTerm 26 August 2019 11:00 AM
1) What is Total Access Communications System. (5)
2) Differnce b/w Intera-PCF and Inter-PCF. (5)
3) Write note on SIFS, PISF, DIFS and EIFS. (5)
4) Write the different Mobile IP Registration Steps. (5)
5) Write Two Benfits of each TDMA and Contention-based MAC Protocol. (5)
6) Explaing ESS and BSS with Diagram. (5)
7) Explaing Flooding and Data Centric Routing in WSN. (10)
8 ) Diagram for below: (10)
-) Data Flow diagram of IEEE 802.15.4 Beacon-enable-mode
-) Data Flow diagram of IEEE 802.15.4 non Beacon-enable-mode
-) Data Flow diagram of IEEE 802.15.4 device to Beacon-enable
9) Snario of adhoc network & required to answer two neighbour hosts. (10)

 

my today paper CS718 26-08-2019

Inter-PCF and Intra-PCF 5

03 Major Subsystem of GSM 05

Tunnelling Process of Mobile IP 05

Power Management , Mobility Management and Task Management 05

05 use cases for wireless meltimedia sensor n/W

AODV if distination path is not available

Three Network abc etc

Three use cases wireless sensor actuator n/w

LEACh engery compuption



 

1 AODV
2 Intra-PFC and inter-PFC
3 3G cdma 2000
4 SPIN
5 WMNs
6 WSANs
7 IEEE 802.11
8 senario base
9 senario base

 

My paper CS718 25/8/19 5:00 pm
Q1: Explain briefly whether Explicit Congestion Notification (ECN) can improve TCP performance in wireless networks or not? Support your answer with logical arguments. 5
Q2: Briefly explain the Active and Hold bluetooth modes. 5
Q3: Briefly explain TACS Total Access Communication System. 5
Q4: Elaborate the Routing Challenges and Design Issues in Wireless Sensor Networks (WSN).5
Q5: Forgot
Q6: Forgot
Q7: Explain the Mobility and Handoff issues in 4G. 10
Q8: What are advantages and disadvantages of transmission power-based scheduling in WCDMA? 10
Q9: Elaborate the critical factors influencing the network performance in Wireless Mesh Networks? 10



 

CS718 Final Term 2018

 

Q: What are three goals of IEEE 802.11 with respect to security? 5

Goals of 802.11 Security:

Access Control:

Ensure that your wireless infrastructure is not used.

Data Integrity:

Ensure that your data packets are not modified in transit.

Confidentiality:

Ensure that the contents of your wireless traffic is not learned

 

Q: What is the difference between Contention based and TDMA protocols? 5

TDMA Protocols Contention Based Protocols
·         These protocols can easily avoid or reduce energy waste from different sources. Contention protocols need to work hard in order to avoid or reduce energy waste.
·         TDMA has limited scalability and adaptivity. These protocols are adaptive than TDMA.
·         It is hard to dynamically change frame size when new nodes join. It can accommodate different slot sizes when new nodes join.
·         TDMA restricts direct communication within a cluster. Contention protocols support multi-hop communications.

 

Q: Describe the Tunneling process of Mobile IP? 5

  • After registration, an IP tunnel is set up between the home agent and care-of address of the mobile node.
  • Home agent broadcasts gratuitous ARP request which causes all nodes in the subnet to update their ARP caches to map the mobile nodes IP address to the home agents link level address.
  • Thus home agent receives packets destined to the mobile node, and forwards the packets to the foreign agent through the IP tunnel.
  • In the foreign network, de-capsulation is done by the foreign agent or by the mobile node itself.
  • A correspondent node assumes that the reply from the mobile node is coming from its home network and continues to send the packet to the home agent.

 

Q: Describe the Registration process of Mobile IP? 5

Mobile node recognizes that it is on a foreign network, acquires a Care-of- Address and requests its home agent to forward its data packets to the foreign agent. The process of registration requires 4 steps:

  • Mobile node request forwarding service by sending registration request to the foreign agent.
  • Foreign agent relays this request to the home agent.
  • Home agent accepts or denies the request and sends registration reply to the foreign agent.
  • Foreign agent relays this reply to Mobile node.

 

Q: Why do we need broadband wireless access? 5

  • To fill the gap between high data rate wireless LAN and very mobile cellular networks.
  • It is a wireless alternative to cable and DSL for last-mile broadband access in developing countries and rural areas.
  • Provide high-speed mobile data and telecommunications services.

 

Q: Make a comparison between 802.11 and 802.16. (5)

802.11 802.16
·         This standard defines Wireless Local Area Network technology based products. It defines WiMAX technology based products.
·         It is optimized for shorter range topologies. It is optimized for longer distances and more difficult environments such as heavily wooded areas.
·         Its coverage range is 30-100 meters Its range is 7-50 Kilometers.
·         It was not designed to serve a large number of users. It is specifically designed to provide service to large number of users.
·         Its designed for indoor use only. Its designed for outdoor use.



Q: In Bluetooth, a device can be associated in two pico-nets at the same time. Is there any
reason why one device cannot be the master in both of them at the same time? 5

If a Bluetooth device is associated in two pico-nets at the same time, the device should jump back and forth between the two hopping sequences of the two pico-nets. In this case, a single Bluetooth device cannot be master in two pico-nets because unique MAC address of the master defines the hopping sequences of the pico-net. If a device is master in both pico-nets, both pico-nets will follow the same sequence which will result in the data corruption of both pico-nets. So a single Bluetooth device cannot be master in two pico-nets.

 

Q: Differentiate between Inter-Mode and Intra-Mode Handover in WCDMA .5

Inter-mode handover

Handover to the UTRA TDD mode.

Dual mode FDD-TDD terminals operating in FDD measure power level from TDD cells available

The TDD CCPCH bursts sent twice during 10ms frame can be used for measurement.

Since TDD cells are synchronized, finding one slot means that other TDD cells have roughly same timing for their burst.

Intra-mode handover

Include soft handover, softer handover and hard handover.

Rely on the Ec/No measurement performed from the CPICH.

 

Q: What are the pros n cons of SPIN (Sensor Protocols for Information via Negotiation)? 5

Pros:

  • Each node only needs to know its one-hop neighbors.
  • Significantly reduce energy consumption compared to flooding.

Cons:

  • Data advertisement cannot guarantee the delivery of data.
  • If the node interested in the data are far from the source, data will not be delivered.

 

Q: What are the pros and cons of Directed Diffusion? 5

Pros:

  • Data centric: All communications are neighbor to neighbor with no need for a node addressing mechanism.
  • Each node can do aggregation & caching.

Cons:

  • On-demand, query-driven: Inappropriate for applications requiring continuous data delivery, e.g., environmental monitoring.
  • Attribute-based naming scheme is application dependent
    • For each application it should be defined a priority
    • Extra processing overhead at sensor nodes

 

Briefly describe the access code types in Bluetooth. (5)

Access code is used for timing synchronization, offset compensation, paging and inquiry. There are three different types of Access code:

  1. Channel Access Code (CAC): It identifies a unique piconet.
  2. Device Access Code (DAC): It is used for paging and its subsequent responses.
  3. Inquiry Access Code (IAC): It is used for inquiry purposes.

 

Q: Differentiate between IEEE 802.11a and IEEE 802.11b. 5

IEEE 802.11a

  • Makes use of 5-GHz band
  • Provides rates of 6, 9, 12, 18, 24, 36, 48, 54 Mbps
  • Uses orthogonal frequency division multiplexing (OFDM)
  • Subcarrier modulated using BPSK, QPSK, 16-QAM or 64-QAM

IEEE 802.11b

  • Provides data rates of 5.5 and 11 Mbps
  • Complementary Code Keying (CCK) modulation scheme

 

Q: What is Piconet? What is the minimum number of devices it support?

piconet is formed when at least two devices, such as a portable PC and a cellular phone, connect. A piconet can support up to eight devices. It is the network formed by a Master and one or more slaves (max 7). Each piconet is defined by a different hopping channel to which users synchronize. Each piconet has maximum capacity of 1 Mbps.

 

Q: Briefly describe the Scatternet. 5

This is an ad-hoc, peer to peer (P2P) network which is used for inter-piconet communication. A scatternet can contain up to 10 piconets. Multiple piconets can operate within the same physical space.

 

Q: How can we distinguish between baseband signal and band pass signal? (5)

  • Baseband Signal is obtained by converting analog or digital data into analog or digital signal, bandwidth = [0, fmax]
  • Band pass Signal is a band-limited signal whose minimum frequency is different from zero, bandwidth = [f1, f2]

 

Q: What is ZigBee Protocol? 5

It is a standard for mesh networking. It provides reliability through meshed connectivity. It is designed for low power applications. It provides very long battery life. But it has low data rate usually 20-250 Kb/sec depending on the band.

It is very secure because it provides AES-128 encryption. It is self-configuring and allows ad-hoc networks. It is very easy to install and configure.

 

Q: Discuss the characteristics of WMN (Wireless Mesh Network). 5

Multi-hop: To extend the coverage range of wireless networks without sacrificing the channel capacity and non-line-of-sight.

Support for ad hoc networking: Due to flexible architecture, easy deployment and configuration, fault tolerance and mesh connectivity is possible. It has low up-front investment requirements.

Mobility dependence on type of mesh nodes: Mesh routers usually have minimal mobility. Mesh clients can be stationary or mobile.

Multiple type of network access: Both backhaul access to internet and P2P communication are supported by WMN. Integration of WMN with other wireless networks allow end-users access to WMN.

 

What are the limitations of TCP for Wireless Sensor Networks and classify the transport protocols for WSN? 5

Following are the reasons due to which TCP protocol is not suited for Wireless Sensor Networks: –

  • Higher overheads for short data transmissions.
  • Flow and congestion control cause unfair bandwidth for farther nodes.
  • Throughput degrades under wireless due to higher packet losses.
  • End-to-end congestion needs longer time to mitigate congestion, causing more congestion to occur.
  • End-to-end reliability consumes more energy and bandwidth than hop-by-hop.
  • TCP provides packet-based reliability, which is not required for event-driven applications.

 

Q: Briefly describe the IEEE 802.11 goals. 5

  • To deliver services in wired networks
  • To achieve high throughput
  • To achieve highly reliable data delivery
  • To achieve continuous network connection.

 

Q: Which protocol is used in WMSN (Wireless Multimedia Sensor Network)? TCP or UDP? 5

Both protocols perform well according to different situations:

  • For real-time applications like streaming media, UDP seems preferred over TCP.
  • Effect of dropping packets is present in UDP which makes it unfavorable to be used in WMSN.
  • WMSNs need support for traffic heterogeneity which is not present in UDP.
  • So TCP with appropriate modifications is preferable over UDP for WMSNs, if standardized protocols are to be used.

 

Q: Describe the major capabilities for mobility in Mobile Ad-hoc NETworks. 5

  • It is a group of mobile, wireless nodes which cooperatively and spontaneously form a network independent of any fixed infrastructure or centralized administration.
  • In MANET, a node communicates directly with nodes within wireless range.
  • A node communicates indirectly with all other destinations using a dynamically determined multi-hop route though other nodes in the MANET.

Q: What are security threats in Sensor Networks? 5

  • Use of wireless communications -In a broadcast medium, adversaries can easily eavesdrop on, intercept, inject and alter transmitted data.
  • Adversaries can interact with networks from a distance by inexpensive radio transceivers and powerful workstations.
  • Resource consumption attacks. Adversaries can repeatedly send packets to drain nodes battery and waste network bandwidth, can steal nodes.
  • However, these threats are not addressed. Focus is on guaranteeing message authenticity, integrity and confidentiality

 

Q: What is the difference between Periodic and Aperiodic signals? 5

Periodic Signal Aperiodic Signal
·         A signal which repeats itself after a specific interval of time is called periodic signal. A signal which doesn’t repeat itself after a specific interval of time is called aperiodic signal.
·         It can be represented by a mathematical equation. It cannot be represented by a mathematical equation.
·         Their value can be determined at any point of time. Their value cannot be determined with certainty at any given point of time.
·         These are deterministic signals. These are random signals.
·         Example: sine waves, cosine waves etc. Example: sound signals from a radio or noise signals

 

Q: Give the specifications of GSM. 5

  • Frequency band: 1,850 to 1,990 MHz (mobile station to base station).
  • Duplex distance: 80 MHz
  • Channel Bandwidth: 200 kHz.
  • Modulation: Gaussian Minimum Shift Keying (GMSK).
  • Transmission Rate: over-the-air bit rate of 270 kbps.
  • Access Method: Time Division Multiple Access (TDMA)
  • Speech Coder: GSM uses Linear Predictive Coding (LPC). Speech is encoded at 13 kbps.

 

Q: Explain briefly whether Explicit Congestion Notification (ECN) can improve TCP performance in wireless networks or not? Support your answer with logical arguments. 5

ECN is an extension proposed to Random Early Detection (RED). It marks a packet instead of dropping in when the average queue size is between minth and maxth. Upon receipt of congestion marked packet, the TCP receiver informs the sender about incipient congestion, which in turn will trigger the congestion avoidance algorithm at the sender.

This process will definitely improve the TCP performance in wireless networks.

 

Q: Differentiate between Zigbee and Bluetooth. 5

Bluetooth (IEEE 802.15.1) Zigbee (IEEE 802.15.4)
·         Data throughput is 1Mbps. Data throughput is less than 0.25 Mbps
·         Suitable applications are Cell phones, computers, PDAs, Printers, Microphones, Speakers, Heandsets, Bar Code Readers, Sensors, Displays, Pagers etc. Suitable applications are Industrial, Agricultural, Vehicular, Residential, Medical applications, Sensors and Actuators with very low power consumption and low cost.
·         QoS needs: QoS suitable for Voice applications. QoS needs: Relaxed needs for data rate and QoS.

 

Q: Write the drawback of S-MAC in WSN. 5

Following are the drawbacks of S-MAC in WSN:

  • Active (Listen) Interval is long enough to handle to highest expected load. If message rate is less, energy is still wasted in idle-listening.
  • S-MAC fixed duty cycle is not optimal.
  • High Latency is another drawback of S-MAC.

 

  1. Brief note on ESS. 5

Answer: An extended service set, consisting of a set of BSSs, must have a common service set identifier (SSID). The BSSs can all work on the same or different channels. This helps to boost the signal throughout the wireless network. For an ESS, the AP includes an Authenticator, and each associated STA includes a Supplicant.

 

Q: Differentiate between GPSS and GPC. 5

Bandwidth Grant per Subscriber Station (GPSS):  Base station grants bandwidth to the subscriber station. Subscriber station may re-distribute bandwidth among its connections, maintaining QoS and service-level agreements.

Bandwidth Grant per Connection (GPC): Base station grants bandwidth to a connection. Higher overhead, but allows simpler subscriber station.

 

Q: Differentiate between Proactive and Reactive Routing Protocols. 5

Proactive Protocols: In networks utilizing a proactive routing protocol, every node maintains one or more tables representing the entire topology of the network. These tables are updated regularly in order to maintain an up-to-date routing information from each node to every other node.

To maintain the up-to-date routing information, topology information needs to be exchanged between the nodes on a regular basis, leading to relatively high overhead on the network. One the other hand, routes will always be available on request. Optimized Link State Routing protocol (OLSR) is an example of the proactive protocols.

Reactive Protocols: Unlike proactive routing protocols, reactive routing protocols does not make the nodes initiate a route discovery process until a route to a destination is required. This leads to higher latency than with proactive protocols, but lower overhead. Ad-Hoc On-Demand Distance-Vector Routing Protocol (AODV) is an example of reactive protocols.

 

Q: Give a brief overview of WiMax. (5)

It is a family of standards for Wireless Metropolitan Area Networks (WMAN). It provides broadband (i.e., voice, data, video) connectivity to various users. It specifies the air interface, including the Medium Access Control (MAC) layer and multiple physical layer specifications. 802.16e is an amendment to 802.16d (fixed or nomadic wireless broadband) to support mobility. It supports vehicular speeds up to 75 mph.

 

Q: Elaborate the critical factors influencing the network performance in Wireless Mesh Networks? 10

Following are the critical issues in mesh network:

  • Different Radio Techniques: Mesh networks include various radio techniques such as MIMO systems and Multi-Radio chipsets. So this requires revolutionary changes in design of higher layers.
  • Scalability: There is multi-hop routing in WMN which degrades performance of the network. Network self-organization and topology control algorithms are needed to increase the performance.
  • Compatibility: Network has to provide connectivity to the conventional clients as well as mesh clients. So this becomes really a headache.
  • Interoperability: Inter-operability of mesh clients and conventional network clients is also a major issue.
  • Security: This is the serious issue of mesh networks due to the involvement of such a large number of computers for routing purposes.

 

Q: Difference between Ad-hoc networks and Cellular network also Characteristics? 10

Ad hoc networks:

  • These networks are infrastructure-less.
  • Multiple hop: Radio power limitation, channel utilization, and power-saving concerns
  • DCF (Distributed Coordination Function)

Characteristics of Ad hoc networks:

  • Heterogeneous nodes can be connected easily.
  • Self – creating: not rely on a pre-existing fixed infrastructure.
  • Self-organizing: no predetermined topology.
  • Self-administering: no central control.
  • Creating a network “on the fly”.

Cellular networks:

  • Infrastructure-based
  • One hop (uplink or downlink)
  • PCF (Pointed Coordination Function)

 

Q: What are advantages and disadvantages of transmission power-based scheduling in WCDMA? 10

Advantages:

  • This scheduling technique minimizes the average power sent per bit.
  • Less interference is faced during transmission under this approach.
  • Power-based scheduling increases the throughput.
  • Users close to the BS get higher bit rate as compared to the others.

Disadvantages:

  • Accurate power estimation is very difficult so wrong estimation can disturb the network communication and resources.
  • Unfair resource allocation is another disadvantage due to wrong power estimation.
  • Users at the edge of the cell get lower bit rate.

 

Q: List and explain the types of link which is established between Master and Slave? 10

  1. Synchronous Connection Oriented (SCO):
  • Allocates fixed bandwidth between point-to-point connection of master and slave.
  • Master maintains link using reserved slots.
  • Master can support three simultaneous links.
  • Bandwidth reservation/QoS.
  • No retransmissions required or done in this mode.
  1. Asynchronous Connection-Less (ACL):
    • Point-to-multipoint link between master and all slaves.
    • Only single ACL link can exist.
    • 1, 3 or 5 slot packets are defined.

 

Q: Power Saving techniques for high rate WPAN? 10

Standard provides three techniques to enable DEVs to turn off for one or more super frames:

DSPS (Device Synchronized Power Save) Mode: Besides allowing the DEVs to wake up and exchange traffic at the same time, the use of DSPS sets makes it easy for other DEVs in the pico-net to determine exactly when a DSPS. DEV will be available to receive traffic.

PSPS (Pico-net Synchronized Power Save) Mode: This mode allows DEVs to sleep at intervals defined by the PNC (Pico-Net Coordinator). The DEV sends a request to the PNC when it wants to enter the PSPS mode.

APS (Asynchronous Power Save) Mode: The only responsibility of a DEV in APS mode is to communicate with the PNC before the end of its ATP (Association Timeout Period) in order to preserve its membership in the pico-net.

 

Q: What is Snooping TCP? Discuss its advantages and disadvantages 10

Snooping TCP: It involves modification of the network layer (IP) software at the base station (BS) by adding a module called snoop. Snooping is the transparent extension of TCP within the BS/FA. Buffering of packets are sent to the mobile host. Lost packets on the wireless link (both directions!) will be retransmitted immediately by the mobile host or foreign agent, respectively (so called local retransmission). The foreign agent therefore snoops the packet flow and recognizes acknowledgements in both directions, it also filters ACKs. Changes of TCP are made only within the foreign agent.

Advantages:

  • The end-to-end TCP semantic is preserved.
  • Most of the enhancements are done in the foreign agent itself which keeps correspondent host unchanged.
  • Handover of state is not required as soon as the mobile host moves to another foreign agent. Even though packets are present in the buffer, time out at the CH occurs and the packets are transmitted to the new COA.
  • No problem arises if the new foreign agent uses the enhancement or not. If not, the approach automatically falls back to the standard solution.

Problems:

  • Snooping TCP does not isolate the behavior of the wireless link as well as l-TCP. Transmission errors may propagate till CH.
  • Using negative acknowledgements between the foreign agent and the mobile host assumes additional mechanisms on the mobile host. This approach is no longer transparent for arbitrary mobile hosts.
  • Snooping and buffering data may be useless if certain encryption schemes are applied end- to-end between the correspondent host and mobile host. If encryption is used above the transport layer, (eg. SSL/TLS), snooping TCP can be used.

 

Q: Write note on SIFS, PISF and DIFS. 10

Short Inter-Frame Space (SIFS): The SIFS is used for the highest-priority transmissions, such as RTS (Request To Send) or CTS (Clear To Send) frames and positive acknowledgments.

PCF Inter-Frame Space (PIFS): The PIFS is used by the PCF during contention-free operation. Stations with data to transmit in the contention-free period can transmit after the PIFS has elapsed and preempt any contention-based traffic.

DCF Inter-Frame Space (DIFS): The DIFS is the minimum medium idle time for contention-based services. Stations may have immediate access to the medium if it has been free for a period longer than the DIFS.

Extended Inter-Frame Space (EIFS): The EIFS is not a fixed interval. It is used only when there is an error in frame transmission.

 

Q: List and explain QoS support at TCP/IP layers at wireless mesh network. 10

Physical Layer:

  • Robust modulation
  • Link adaptation

MAC Layer:

  • Offer priorities
  • Offer guarantees (bandwidth, delay)

Network Layer:

  • Select good routs
  • Offer priorities
  • Reserve resources (for guarantees)

Transport:

  • Attempt end-to-end recovery when possible

Application:

  • Negotiate end-to-end and with lower layers
  • Adapt to changes in QoS

 

Q: Elaborate the compressed mode measurement and classify its methods? 10

Compressed Mode Measurements:

  • The compressed mode is needed when making measurement from another frequency without full dual receiver terminal.
  • The intention is not to lose data but to compress.
  • The transmission and reception are halted for a short time to perform measurements on the other frequencies.

Three methods for compressed mode:

  1. Lowering the data rate from higher layers because they have knowledge of compressed mode schedule.
  2. Lowering the data rate by changing the spreading factor.
  3. Reducing the symbol rate by puncturing at the physical layer multiplexing chain but limited to rather short Transmission Gap Lengths (TGL).

 

Q: What is the difference between WMN (Wireless Mesh Network) and MANET (Mobile Ad-hoc NETwork)? 10

  • WMNs require more sophisticated algorithms and design principles but MANET requires less complicated algorithms.
  • Mesh routers as wireless backbone provide more coverage, connectivity and robustness. Individual nodes are routers in MANET making unreliable.
  • MANET supports client that use the same radio technology. Which is accomplished through host-routing function available in mesh router.
  • In MANET, each host perform routing and configurations which is done by mesh routers in WMNs. Hence decreasing load on end-user.
  • WMN uses two radios; one for routing and configuration functionalities between mesh routers and second radio for network access by end users. These are performed on same channel in MANET. This significantly improves the performance.
  • Hosts also working as router in MANET make it more challenging, where the mobility of mesh routers is very limited

 

Q: WiMax Network Architecture diagram? 10

 

Q: List the functionalities of the following sub-layers of the WiMAX MAC layer: 10

  1. MAC common part sub-layer
  2. Privacy sub-layer
  3. MAC Common Part Sub-Layer: This layer performs core MAC functionalities such as:
    • Scheduling
    • Connection maintenance
    • Fragmentation
    • QoS control
  4. Privacy Sub-Layer: This layer has following functionalities:
    • Encryption
    • Authentication
    • Secure key exchange

 

Q: List and briefly explain four differences between Wireless Sensor Networks and other Wireless Ad-hoc Networks. 10

Scalability: The number of nodes in a wireless sensor network can be several orders of magnitude higher than the nodes in an ad hoc-network.

Deployment: Sensor nodes are densely deployed but ad-hoc nodes are not deployed densely.

Failure Rate: Sensor nodes are prone to failures as compared to the ad-hoc nodes.

Highly Dynamic Topology: The topology of a sensor network changes very frequently but in case of ad-hoc network, it doesn’t change so frequently.

Communication Paradigm: Sensor nodes mainly use broadcast whereas most ad-hoc networks are based on peer to peer.

Power Limitation: Sensor nodes are limited in power, computational capacities and memory. On the other hand, these limitations are not imposed on the ad-hoc nodes.
Unique IDs: Sensor nodes may not have global ID but ad-hoc nodes may have global ID.

 

Q: What are advantages and disadvantages of Indirect TCP II? (10)

Advantages:

  • No changes in the fixed network necessary, no changes for the hosts (TCP protocol) necessary, all current optimizations to TCP still work.
  • Transmission errors on the wireless link do not propagate into the fixed network.
  • Simple to control, mobile TCP is used only for one hop between, e.g., a foreign agent and mobile host.
  • Therefore, a very fast retransmission of packets is possible, the short delay on the mobile hop is known.

Disadvantages:

  • Loss of end-to-end semantics, an acknowledgement to a sender does not any longer mean that a receiver really got a packet, foreign agents might crash
  • higher latency possible due to buffering of data within the foreign agent and forwarding to a new foreign agent

 

Q: Draw time-line diagrams for the following: 10

  1. Data transfer in IEEE 802.15.4-based network from a device to coordinator in a beacon-enabled mode.
  2. Data transfer in IEEE 802.15.4-based network from a device to coordinator in a non-beacon-enabled mode.
  3. Data transfer in IEEE 802.15.4-based network from a coordinator to device in a beacon-enabled mode.
  4. Data transfer in IEEE 802.15.4-based network from a coordinator to device in a non-beacon-enabled mode.

 

Q: Draw a Scatternet architecture consisting of three piconets with maximum number of slave nodes in each piconet. 10

Q: What are the security flaws in WEP? 10

  • Physical threats: User who loses 802.11 NIC, does not report it. On the other hand, attacker with physical possession of NIC may be capable of accessing the network.
  • Impersonation: User Identification: 811 does not identify users, only NICs are identified. Due to this problem, MAC may represent more than one user.
  • Mutual Authentication: 11 shared authentication not mutual. Client authenticates to Access Point but Access Point does not authenticate to client. It enables rogue access points which may cause denial of service attacks possible.
  • Known Plaintext Attack: WEP supports per-packet encryption, integrity, but not per-packet authentication.
  • Denial of Service: Disassociation Attacks:11 associate/disassociate messages unencrypted and unauthenticated. It enables forging of disassociation messages. It also creates vulnerability to denial of service attacks.
  • Dictionary Attacks: WEP keys are derived from passwords that makes it much easier to break keys by brute force. Attacker uses a large list of words to try to guess a password and derive the key.

 

Q: What are Packet Scheduling Algorithms? Give their advantages. 10

In WCDMA packet scheduling algorithms can be done in two ways, in a time or code division manner.

Time Division Scheduling: In time division scheduling, one user is allocated a channel at a time (10 ms frame). All available capacity can be allocated to that user. It provides high data rate for a short period of time.

Advantages of Time Division Scheduling:

  • High bit rate required less energy per bit.
  • Less interference
  • Shorter delay due to high bit rate.

Code Division Scheduling: Many users are allocated the channels simultaneously in code division scheduling. It provides low data rate for a long period of time. So if we increase more users, each user’s bit rate is decreased.

Advantages of Code Division Scheduling:

  • Resources are in full usage due to longer transmission time
  • Small variation in interference level

 

Q: Give IEEE 802.15.3 Super frame format and discuss its parts super frame # in detail with its format? 10

Super frame is composed of following three parts:

  • The Beacon: Which is used to set the timing allocations and to communicate management information for the piconet.
  • The Contention Access Period (CAP): Which is used to communicate commands and/or asynchronous data if it is present in the super frame.
  • The Channel Time Allocation Period (CTAP): Which is composed of channel time allocations (CTAs), including management CTAs (MCTAs).

Super Frame format is given below:

 

Q: Give Three reason each for non-suitability of TCP and UDP for WSN. (10)

Reasons of non-suitability of TCP:

  • Higher overheads for short data transmissions.
  • Flow and congestion control cause unfair bandwidth for farther nodes.
  • Throughput degrades under wireless due to higher packet losses.
  • End-to-end congestion needs longer time to mitigate congestion, causing more congestion to occur.
  • End-to-end reliability consumes more energy and bandwidth than hop-by-hop.
  • Packet-based reliability, which is not required for event-driven applications

Reasons of non-suitability of UDP:

UDP has lower over overheads as compared to TCP but still it is not suitable for WSN due to the following reasons:

  • No congestion control
  • No flow control
  • No reliability

 

  1. What is channelization? When two cells used same code what is happens. Give the solution of problem.? 10

Channelization: It is the process of increasing signal bandwidth by using orthogonal codes. Channelization codes are orthogonal codes, based on Orthogonal Variable Spreading Factor (OVSF) technique. The codes are fully orthogonal, i.e., they do not interfere with each other, only if the codes are time synchronized. Thus, channelization codes can separate the transmissions from a single source. In the downlink, it can separate different users within one cell/sector. Limited orthogonal codes must be reused in every cell.

Problem: Interference if two cells use the same code

Solution: Scrambling codes to reduce inter-base-station interference.

It is possible that two mobiles are using the same codes. In order to separate different users in the uplink, scrambling codes are used. One code tree is used with one scrambling code on top of the tree.

 

Q: Categorize Handoff Types in 4 G and what are Vertical Handoff issues? 10

There are two types of handoffs in 4G: –

Homogeneous (Horizontal) Handovers:

  • Homogeneous Handovers are made within single network (Localized Mobility).
  • These handovers have limited opportunities.
  • They mainly use received signal strength (RSS) to decide handoff.

Heterogeneous (Vertical) Handovers:

  • Vertical handovers are made across different networks (Global Mobility).
  • There are more opportunities of heterogeneous handovers.
  • They use RSS, offered bandwidth, price, power consumption, speed to decide handover.

VHO Issues:

  • The main issue is to decide when to switch?
  • Next issue is the development of VHO policies.
  • Switching from WLAN to cellular is not the same as switching from cellular to WLAN.
  • Provision of seamless handoff is another issue of VHO.
  • Packet loss and VHO latency is also an issue.
  • Load balancing between networks.
  • To provide QoS guarantees
  • Security and Authentication.
  • Billing

 

Q: Explain the Factors influencing sensor network design. 10
Fault Tolerance:
Fault tolerance is the ability to sustain sensor network functionalities without any interruption due to sensor node failures. The fault tolerance level depends on the application of the sensor networks.
Scalability: Scalability measures the density of the sensor nodes.

Production Costs: The cost of a single node is very important to justify the overall cost of the networks.
The cost of a sensor node is a very challenging issue given the amount of functionalities with a price of much less than a dollar.
Hardware constraints: Different types of hardware is a big factor which influences the sensor network design.

Sensor network topology:
Pre-deployment and deployment phase
Post-deployment phase
Re-deployment of additional nodes phase
Power consumption:
Sensing
Communication
            Data processing

Environment:
Busy intersections
Interior of a large machinery
Bottom of an ocean
Inside a twister
Biologically or chemically contaminated field
Battlefield beyond the enemy lines
Home or a large building
Large warehouse
Fast moving vehicles
Drain or river moving with current.

 

Q: Write a note on communication architecture of sensor networks.

  • Data link layer: The data link layer is responsible for the medium access and error control. It ensures reliable point-to-point and point-to-multipoint connections in a communication network.
  • Medium access control: It is responsible for creation of the network infrastructure. It fairly and efficiently shares communication resources between sensor nodes.
  • Power saving modes of operation: Operation in a power saving mode is energy efficient only if the time spent in that mode is greater than a certain threshold.
  • Error control:
    • Forward Error Correction (FEC)
    • Automatic Repeat Request (ARQ).
    • Simple error control codes with low-complexity encoding and decoding might present the best solutions for sensor networks.

 

Q: What are different Bluetooth connection state?

Active Mode: In this mode, device participates actively on the transmission channel. The master regularly sends a packet to the slaves (polling) to enable the slaves to be able to send a packet to the master and re-synchronize themselves

Sniff Mode: This is a low consumption mode. A Bluetooth module in the Sniff mode stays synchronized in the piconet. It listens to the piconet at regular intervals (Tsniff) for a short instant on specified slots for its message.

Hold Mode: The module remains synchronized. This is lower consumption mode than the Sniff mode. Only the counter on the Bluetooth chip in hold mode is active. At the end of the Hold period, the Bluetooth module returns to the active mode.

Park Mode: A Bluetooth module in this mode is no longer an active member of the piconet. However, it remains synchronized with the master and can listen to a broadcast channel (Beacon Channel).

 

Q: Describe major characteristics of Bluetooth.

  • It supports connections types of Spread Spectrum and Time Division Duplex.
  • It uses 2.4 GHz ISM Open Band spectrum.
  • Its modulation technique is Gaussian Frequency Shift Keying
  • Transmission power is 1mw – 100 mw
  • Bluetooth has the data rate of 1 Mbps.
  • Its range is 30 feet.
  • It supports maximum 8 devices at a time.
  • It provides 128 bit Data Security Authentication Key.
  • It uses encryption key of 8-128 bit.
  • Its module size is 9 x 9 mm.
  • Headset Profile
  • Dial-up Networking Profile
  • Fax Profile
  • LAN Access Profile
  • Generic Object Exchange Profile
  • Object Push Profile
  • File Transfer Profile
  • Synchronization Profile



Questions No 2

Traffic Data access in WCDMA

Types of Data Packet Traffic

  • Packet data traffic is a non-real-time packet services including Interactive and Background traffic classes. Their properties are

 Packet data is busty. Sometimes a large amount of data is transferred. At the other times no data is sent. Thus, the required bit rate can change rapidly.

 Packet data tolerates longer delay than real-time services. It is controllable traffic from the RNC; thus, RNC can decide when and how to send the data.

 Packets can be transmitted by the radio link control layer which provides retransmission and error correction services. Therefore, it allows high frame error rate with low transmission power.

  • One example of packet data traffic is ETSI packet data model for web browsing.
  • Characteristics of packet service session

 Session arrival process, number of packet calls per session, reading time, number of packets within a call, inter-arrival time in a call, packet size.

 

Question No

WCDMA packet Access

  • In WCDMA packet allocations, e.g., time and bit rate, are controlled by the packet scheduler (PS) located in RNC. PS functions include:

Properly allocate the available resources (time, code or power) between the packet data users

Decide the allocated bit rates and the length of the allocation

Decide to use the transport channel

Monitor the packet allocations and the systems loads

  • PS can allocate common, dedicated or shared channels to packet data users. It can also change the bit rate during active connection.
  • PS can increase or decrease the network load by increasing or decreasing the bit rates of the packet bearers respectively.

 

Question

ESS

  • Access Point functions as a bridge and a relay point.
  • In BSS, MS communicate through Access Point
  • IBSS is typically an ad hoc network, where station communicate directly.
  • To integrate 802.11 with 802.2 (Wired LAN), a portal is used.
  • Portal is a device such as bridge or router attached to DS.

 

Messages Distribution in ESS

  • Two services involved in distribution of messages within DS.
  • Distribution

Primary service used to exchange MAC frames between stations of two BSSs.

Source sends to AP of one BSS, which sends to DS. DS then sends to AP of the destination.

Message transport in DS is beyond the scope of IEEE 802.11 standard.

  • Integration

Enables transfer of a data between a station on an IEEE 802.11 LAN and a station on an integrated IEEE 802.x LAN (Wired LAN).

It takes care of any address translation and media conversion logic

 

 

Question No

Bluetooth protocols

  • Service Discovery Protocol (SDP)

 Defines a service record format

Information about services provided by attributes

Attributes composed of an ID (name) and a value

IDs may be universally unique identifiers (UUIDs)

  • Defines an inquiry/response protocol for discovering services

 Searching for and browsing services

  • RFCOMM (based on GSM TS07.10)

 Emulates a serial-port to support a large base of legacy (serial-port-based) applications

 Allows multiple 􀍞ports􀍟 over a single physical channel between two devices

  • Telephony Control Protocol Spec (TCS)

 Call control (setup & release)

 Group management for gateway serving multiple devices

  • Legacy protocol reuse

Reuse exiting protocols e.g WAP, OBEX

 

Overwier of MAC protocol

 

Question

Energy Efficiency in MAC Design

  • Energy is primary concern in sensor networks
  • What causes energy waste?

Collisions

Control packet overhead

Overhearing unnecessary traffic

Overemitting

Long idle time Dominant in sensor nets

bursty traffic in sensor-net apps

Idle listening consumes 50—100% of the power for receiving (Stemm97, Kasten)

 

Question NO

Traffic-Adaptive MAC (TRAMA) 10

  • Time is divided into random-access and scheduled-access (transmission) periods.
  • The random-access period is used to establish two-hop topology information
  • MAC layer can calculate the transmission duration needed, which is denoted as SCHEDULE_INTERVAL
  • the node calculates the number of slots for which it will have the highest priority among two hop neighbors
  • The node announces the slots it will use as well as the intended receivers for these slots with a schedule packet.
  • the node announces the slots for which it has the highest priority but it will not use
  • The schedule packet indicates the intended receivers using a bitmap whose length is equal to the number of its neighbors
  • Advantages

Higher percentage of sleep time and less collision probability are achieved, as compared to CSMA-based protocols.

Since the intended receivers are indicated by a bitmap, less communication is performed for the multicast and broadcast types of communication patterns, compared to other protocols.

  • Disadvantages

Transmission slots are set to be seven times longer than the random-access period. This means that without considering the transmissions and receptions, the duty cycle is at least 12.5 percent (idle time),

 

Introduction to WSNs
• A sensor network is composed of a large number of sensor nodes, which are densely deployed
either inside the phenomenon or very close to it.
• Features:
üRandom deployment
üSelf-organizing
üCooperative capabilities
üLocal computation

 

Question No

Handoff
• Intra-PCF
üSupported by A8/A9 interfaces carrying user traffic and signaling between BS and PCF
• Inter-PCF and Intra-PDSN
üOn location change, must occur when causes to divert the packet data session from one R-P interface to another
üNew R-P connection between target PCF and serving PDSN is established and PPP session will be moved to this
üPrevious R-P session tear down
üPCF-PCF handoff may occur while MS is in active or dormant state
üDormant handoff is supported to maintain PPP session, where a MS is dormant to minimize the use of air-link resources.

üDuring active session, PDSN supports low-latency handoff by bi-casting data to the target and previous PCF
• Inter-PDSN
üA network based on simple IP does not support mobility beyond a PDSN coverage area because New IP will be acquired from new PDSN and traffic on existing IP will be undeliverable.Needs to support fast handoff i.e. Mobile IP
• Inter-PSDN Fast Handoff
üThe target PDSN initiates establishment of a P-P session with the serving PDSN.
üP-P interface is used to keep PPP session anchored when PDSN to PDSN
handoff is performed allowing existing PPP session to continue and reducing
service interruption time and data loss

Question No

Multi-radio Unification Protocol
• Discovering neighbours.
üAfter the discovering procedures, neighbours are classified into MUP enabled and legacy
nodes.
• Selecting a NIC
üBased on one-hop round trip time (RTT) measurements. MUP selects the NIC with the shortest RTT between a node and its neighbors.
• Utilizing the selected NIC for a long period.
üThis period is determined by a random process and in the order of 10–20 s.
• Switching channels.
üAfter the random time period, all NICs are measured again through one-hop probe
messages. If an NIC has a certain amount of quality improvement than the existing NIC,
then it is selected for sending packets.

 

Question No

Issues in 4G
• Need to resolve issues as
üAccess
üHandoff
üLocation coordination
üResource coordination to add new users
üSupport for multicasting
üSupport for quality of service
üWireless security and authentication
üNetwork failure and backup
üPricing and billing.

Question No

Mobility Management
• Location Management: enables system to track location of mobile terminal (MT)
üLocation updates and paging
• Handoff Management: the process by which an MT keeps its connection when it moves from
one point of attachment (base station or access point) to another

 

Question No

Heterogeneous Wireless Networks
• A mixture of co-existing radio access technologies.
• Different access technologies (radio interfaces) and overlapping coverage.
• Different network architectures and protocols for transport, routing and mobility management.
• Different service demands from mobile users (low-data rate, high-data rate, voice, multimedia,
etc)
• Different operators in the market.

Question No

Issues in Heterogeneous Wireless Networks
• Bit Error Rate (BER):
ü10 or worse are possible upon change in wireless environment
• Bandwidth
üVery less as compared to wired networks
üTCP underestimated bandwidth in wireless networks
• Round Trip Time (RTT):
üThe wireless media exhibits longer latencies due to long distances or NLOS path.
üLarge variation in RTT in wireless networks
• Mobility:
üAddition of mobile devices introduces huge amount of indeterminate delay in rather a stationary network.
• Power consumption

 

In order to support mobility, Mobile IP includes three capabilities:
1. Discovery
Mobile Agents send ICMP router advertisements with mobility agent advertisement extension periodically informing mobile nodes of its presence.
Mobile node is responsible for the discovery process.
In order to receive an advertisement, the mobile node may optionally request one from an agent or simply wait for the next advertisement.
2. Registration
o Mobile node recognizes that it is on a foreign network, acquires a Care-ofAddress and requests its home agent to forward its data packets to the foreign agent.
The process of registration requires 4 steps:
i. Mobile node request forwarding service by sending registration request to the foreign agent.
ii. Foreign agent relays this request to the home agent.
iii. Home agent accepts or denies the request and sends registration reply to the foreign agent.
iv. Foreign agent relays this reply to Mobile node.
3. Tunneling
o After registration, an IP tunnel is set up between the home agent and care-ofaddress of the mobile node.
o Home agent broadcasts gratuitous ARP request which causes all nodes in the subnet to update their ARP caches to map the mobile nodes IP address to the home agents link level address.
o Thus home agent receives packets destined to the mobile node, and forwards the packets to the foreign agent through the IP tunnel.
o In the foreign network, decapsulation is done by the foreign agent or by the mobile node itself.
o A correspondent node assumes that the reply from the mobile node is coming from its home network and continues to send the packet to the home agent.

Question No

Access and Privacy Services IEEE802
• Authentication
üEstablishes the identity of stations.
üHowever, IEEE 802.11 requires mutually acceptable, successful authentication before association.
• De-authentication
üInvoked to terminate existing authentication
• Privacy
üStandard provides optional use of encryption to assure privacy

 

Q: Define Following Terms:

  1. Packet level QoS: applies to jitter, throughput, and error rate. Network resources such as buffer space and access protocol are likely influences
  2. Circuit level QoS: describes both the time it takes to complete a transaction and the packet loss rate. Certain transactions may be time sensitive, while others cannot tolerate any packet loss.
  3. Channel level QoS: includes call blocking for new as well as existing calls. It depends primarily on a network’s ability to establish and maintain the end-to-end circuit.
  4. Use level QoS: depends on user mobility and application type. The new location may not support the minimum QoS needed, even with adaptive applications.

 

Question NO

IP over Bluetooth

 

Question No

Bluetooth Security

 

 

WiMAX Basics 5
WiMAX or 802.16 is an effort by the IEEE to develop a standards based air interfaces for the licensed and unlicensed radio frequencies from 2 to 66 GHz. The approach they have taken is to develop a common MAC – Media Access Control sub layer of the data link layer. Then to offer differing physical layers to accommodate the needs of the different frequencies and regulatory environments. The IEEE believes that the existing approaches to delivering wireless data services do have the potential for long term growth when used outside of the local area network.

Question No

Design Considerations of WMSN
• Application-specific QoS requirements
üSnapshot and Streaming multimedia
üFlexible architecture to support heterogeneous applications
• Multimedia source coding
üintra-frame/inter-frame
üdistributed source coding
• Multimedia in-network processing
• Multimedia coverage model development
• Power consumption

 

Question No

T-MAC: Choosing TA
• Requirement: a node should not sleep while its neighbors are communicating, potential next
receiver
• TA > C+R+T
üC – contention interval length;
üR – RTS packet length;
üT – turn-around time, time bet. end of RTS and start of CTS;
• TA = 1.5 * (C+R+T);
• Pros
üPerforms better under variable traffic load
• Cons
üHigher overheads than SMAC to maintain variable wakeup schedule.
üUnfairness and unpredictable delay.

 

Question No

TCP Slow Start
• Sender calculates a congestion window for a receiver
• Start with a congestion window size equal to one segment
• Exponential increase of the congestion window up to the congestion threshold, then linear
increase
• Missing acknowledgement causes the reduction of the congestion threshold to one half of the
current congestion window
• Congestion window starts again with one segment

Question No

IEEE 802.11
• A family of standards define Phy and MAC
• IEEE 802.11:
ü Infrared (IR)
ü 2.4Ghz ISM band with 1 or 2 Mbps
• IEEE 802.11b: 11 Mbps in 2.4 GHz
• IEEE 802.11a: 54 Mbps in 5.7 GHz
• IEEE 802.11g: 54 MHz in 2.4 GHz
• IEEE 802.11i: Security
• IEEE 802.11e: QoS
• IEEE 802.11f: Inter-access point protocol

 

Question No

IEEE 802.15.3 – Overview

  • High data rate WPAN
  • Potential future standard
  • Motivation: Data, High quality TV, Home cinema
  • Dynamic topology

 Mobile devices often join and leave the piconet

 Short connection times

  • Multiple Power Management modes
  • Secure Network
  • 2.4 GHz PHY

 4 channels (high density) or 3 channels (with 802.11b) modes are available

  • Supports 5 data rates

 11Mbps(QPSK)

 22Mbps(DQPSK without coding)

 33Mbps(16QAM)

 44Mbps(32QAM), 55Mbps(64QAM)

  • Based on piconets in a person space analogous to LAN in larger area
  • Data Devices (DEV) establish peer-to-peer communication
  • Includes also a Piconet Coordinator (PNC)

 PNC manages the quality of service (QoS) requirements, power save modes and access control to the piconet.

  • A new piconet created with same channel as of the existing PNC is called child/neighbor piconet

 If channel access is also controlled by the parent PNC then it is called dependent piconet

 

ZigBee/IEEE 802.15.4 Market Feature

  • Low power consumption
  • Low cost
  • Low offered message throughput
  • Supports large network orders (<= 65k nodes)
  • Low to no QoS guarantees
  • Flexible protocol design suitable for many applications

 

Question No

Adaptive Burst Profiles

  • Burst profile

 Modulation and FEC

  • Dynamically assigned according to link conditions

 Burst by burst, per subscriber station

 Trade-off capacity vs. robustness in real time

  • Roughly doubled capacity for the same cell area
  • Burst profile for downlink broadcast channel is well-known

 

4G Overview

  • 4G mobile communication systems tend to mean different things to different people:

 For some it is merely a higher-capacity new radio interface,

 While for others it is an inter-working of cellular and wireless LAN technologies that employs a variant of the Mobile IPv6 mobility management protocol for inter-system handoff.

  • There is no doubt that 4G systems will provide higher data rates. Traffic demand estimates suggest that, to accommodate the foreseen amount of traffic in the 2010 – 2020 timeframe in an economically viable way, 4G mobile systems must achieve a manifold capacity increase compared to their predecessors.
  • researchers and vendors are expressing a growing interest in 4G wireless networks that support global roaming across multiple wireless and mobile networks
  • There are many wireless network technologies Cellular networks, Wireless LANs, Wireless PANs, mobile Wimax, etc.
  • 4G networks will play a key role for integrating various network architectures and technologies and achieving a seamless wireless access infrastructure
  • 4G provides high-speed, large volume, good quality, and global coverage to roam between different types of technologies
  • It is widely accepted that the individual (wireless and/or wireline) access networks will interface to core and/or backbone network elements over the IP protocol

 

Question No

QoS

  • Supporting QoS in 4G networks will be a major challenge due to varying bit rates, channel

characteristics, bandwidth allocation, fault-tolerance levels, and handoff support among

heterogeneous wireless networks.

  • QoS support can occur at the

 Packet,

 Transaction

 Circuit

 User

  • Packet-level QoS

 Applies to jitter, throughput, and error rate.

 Network resources such as buffer space and access protocol are likely influences.

  • Transaction-level QoS

 Describes both the time it takes to complete a transaction and the packet loss rate.

 Certain transactions may be time sensitive, while others cannot tolerate any packet loss.

  • Circuit-level QoS

 Includes call blocking for new as well as existing calls.

 It depe􀅶ds p􀆌i􀅵a􀆌il􀇇 o􀅶 a 􀅶et􀇁o􀆌k􀍛s a􀄏ilit􀇇 to esta􀄏lish a􀅶d 􀅵ai􀅶tai􀅶 the e􀅶d-to-end

circuit.

  • User-level QoS

 Depends on user mobility and application type.

 The new location may not support the minimum QoS needed, even with adaptive applications.

 

Question No

QoS Parameters

  • 802.11e

 Nominal MSDU size

 Min/mean/max data rate

 Mean/max service interval

 Traffic type (isochronous, asynchronous)

 Burst size

  • UMTS (Release 5)

 Traffic class (conversational, streaming, interactive, or background)

 Guaranteed, maximum bit rate

 Maximum SDU size

 SDU/bit error ratio

 Transfer delay

  • 802.16-2004

 Traffic priority

 Maximum sustained traffic rate

 Maximum traffic burst

 Minimum reserved traffic rate

 Scheduling type (best-effort, non-real time polling, real-time polling, unsolicited grant)

 Tolerated jitter, maximum latency

 

Question NoEnding procedure of pick net

If the PNC is going to stop operation and there are no other PNC capable DEVs in the piconet, the PNC

places the PNC Shutdown information element (IE) into the beacon to notify the members of the piconet.

► In the case that the PNC abruptly leaves the piconet without handing over control to another PNC capable DEV in the piconet, the piconet stops operation.

► After the association timeout period (ATP) expires, a PNC capable DEV from the old piconet will be able to start a new piconet using the normal process,

► In the case of dependent piconets, the parent PNC is able to end the dependent piconet via the Disassociation Request command.

 

Question No Discuss the current challenges in WSN? 5 (From Lecture 34)

Cross-layer approach: A Grand Challenge

Traditional layered approach is not suitable for WSNs

Good for design, abstraction & debugging

Bad for energy efficiency, overhead &

How to realize mapping?

User/Applications Requirements 

► Arch. & Topology or Communication Protocols

► E.g. reliability ?

 

Question No. Describe traffic adaptive MAC protocol with its advantages and disadvantages? 10 (From Lecture 35)

 

Time is divided into random-access and scheduled-access (transmission) periods.

The random-access period is used to establish two-hop topology information

MAC layer can calculate the transmission duration needed, which is denoted as SCHEDULE_INTERVAL

the node calculates the number of slots for which it will have the highest priority among two-hop neighbours

The node announces the slots it will use as well as the intended receivers for these slots with a schedule packet.

the node announces the slots for which it has the highest priority but it will not use

The schedule packet indicates the intended receivers using a bitmap whose length is equal to the number of its neighbours

 

Advantages

► Higher percentage of sleep time and less collision probability are achieved, as compared to CSMA-based protocols.

► Since the intended receivers are indicated by a bitmap, less communication is performed for the multicast and broadcast types of communication patterns, compared to other protocols.

Disadvantages

► Transmission slots are set to be seven times longer than the random-access period. This means that without considering the transmissions and receptions, the duty cycle is at least 12.5 percent (idle time).

 

 

Question No.     GSM

GSM uses several identifiers for

  • the routing of calls,
  • identifying subscribers (e.g. for charging),
  • locating the HLR, identifying equipment, etc.
  • International Mobile Subscriber Identity (IMSI)
  • It is embedded on the SIM card and is used to identify a subscriber.
  • The IMSI is also contained in the subscription data in the HLR.
  • Roaming charging – a VPLMN uses the IMSI to send billing records to the HPLMN of a subscriber.

 

Question No.

Carrier and Information Signals

• Carrier signal: In radio frequency systems an analog signal is always used as the main

airborne signal

• Information Signal: On top of this signal another signal, analog or digital, is added that

carries the information

• Modulation: This combination of signals is called the modulation

• Modulation is why a perfect sine wave is desired

• Modulators superimpose the information onto the sine wave by making tiny modifications

to the sine wave

• If the sine wave is not perfect, these small changes may be lost by the time the signal

gets to the other end of the link

 

  1. Q. TinyOS:

The role of any operating system (OS) is to promote development of reliable application software by providing a convenient and safe abstraction of hardware resources.

Wireless sensor networks (WSNs) are embedded but general-purpose, supporting a variety of applications, incorporating heterogeneous components, and capable of rapid deployment in new environments

An open-source development environment

► A programming language and model (NesC)

TOSSIM for simulating TinyOS

TinyDB for Sensor DB in TinyOS

 

Question No.

Disadvantages of wireless communication

Some disadvantages of wireless communication include a limited amount of bandwidth for communication and breaches of network security. Wireless transmissions can be seen or heard by others on the network, unless security is set so that only registered devices within the network are able to receive data.

Loss

  • All components exhibit one of two properties: Loss or Gain
  • If the signal coming out is smaller than the signal going in, it is loss that appears as heat
  • Attenuators produce loss

Gain

  • If the signal gets larger before it exits the device, it is gain
  • RF amplifiers produce gain
  • Gain is an active process in most cases, in other words it requires a power source
  • Gain can also be the combination of signals from different directions appearing together, such as the main signal and a reflected signal
  • However, the total gain cannot exceed the original level transmitted from the antenna in such a case

 

FDMA

  • FDMA was the initial multiple-access technique for cellular systems
  • Separates large band into smaller channels.
  • Each channel has the ability to support user.
  • Guard bands are used to separate channel preventing co-channel interference
  • Narrow bandwidth (30 khz).

TDMA

  • Entire bandwidth is available to the user for finite period of time.
  • Users are allotted time slots for a channel allowing sharing of a single channel.
  • Requires time synchronization.
  • Each of the user takes turn in transmitting and receiving data in a round robin fashion.

CDMA

  • CDMA is a spread spectrum technique used to increase spectrum efficiency.
  • SS has been used in military applications due to anti-jamming and security.

Advantages

Greatest spectrum efficiency:

CDMA improves call quality by filtering out background noise, cross-talk, and interference

Simplified frequency planning – all users on a CDMA system use the same radio frequency spectrum.

Random Walsh codes enhance user privacy; a spread-spectrum advantage

Precise power control increases talk time and battery size for mobile phones

  • Disadvantages

Backwards compatibility techniques are costly

Currently, base station equipment is expensive

Low traffic areas lead to inefficient use of spectrum and equipment resource

 

TACS

 Total Access Communications System

  • A variant of AMPS developed by Motorola.
  • It has been used in some European countries (including the UK & Ireland), as well as

Japan and Hong Kong.

  • ETACS was an extended version of TACS with more channels.
  • The last ETACS service operated by Vodafone was discontinued on 31 May 2001

Limitations of 3G

  • Difficulty of CDMA to provide higher data rates
  • Need for continuously increasing data rate and bandwidth to meet the multimedia requirements
  • Limitation of spectrum and it‘s allocation
  • Inability to roam between different services
  • To provide a seamless transport end-to-end mechanism
  • To introduce a better system with reduced cost

 

Co-channel interference and system capacity

  • Co-channel cells: cells that use the same set of frequencies and interference is called co-channel interference
  • By increasing SNR, co-channel can not be combated
  • To reduce it, co-channel cells must be separated by a min distance
  • When size of each cell is approximately same and BS transmit at same power, cochannel interference ratio is independent of transmission power and is a function of radius of cell (R) and distance between centers of nearest co-channel cell (D)
  • By increasing the ratio of D/R,

Separation between co-channel cells relative to coverage distance of a cell is increased.

Thus interference is reduced.

 

Adjacent channel interference

  • Interference resulting from signals which are adjacent in frequency
  • It results from imperfect receiver filters which allow nearby frequencies to leak into passband
  • It is more serious if the transmitter is more close to the user‘s receiver listening to desired channel
  • This is near-far effect

A nearby transmitter captures the receiver of subscriber.

Or mobile close to BS transmits on adjacent channel to one being used by a weak mobile

  • Adjacent channel interference can be minimized by careful filtering and channel Assignment

 

Trunking

  • Allows a large number of users to share a small number of channels
  • Channel allocated per call basis from a pool of available channels
  • Relies on statistical behavior of users so that a fixed number of channels (circuits) may accommodate a large random user community
  • Trunking theory is used to determine number of channels for particular area (users)
  • Tradeoff between the number of available channels and likelihood of call blocking during peak calling hours

 

Traffic intensity

  • Traffic intensity is measured as call request rate multiplied by call holding time

User traffic intensity of Au Erlang is (1) Au= λH

Where H is average call duration or holding time and λ is average number of call  requests.

For system of U users and unspecified channels, the total offered traffic intensity A is (2) A = UAu

In a C channel trunked system, traffic equally distributed, traffic intensity per channel Ac

(3) Ac= UAu/C

 

Block Calls Cleared

  • User is given immediate request if a channel is available.
  • If no channel available, the requesting user is blocked and free to try later
  • Assume call arrivals as Poisson Distribution
  • the Erlang B formula determines the probability that call is blocked with no queuing, is a measure of GOS for trunked system

 

Block Calls Delayed

  • Queue is provided to hold blocked calls.
  • Call request may be delayed until a channel becomes available
  • Its measure of GOS is defined as the probability that a call is blocked after waiting specific length of time in the queue
  • The likelihood of a call not having immediate access is determined by Erlang C formula

 

Drawbacks of CDMA Cellular

  • Self-jamming

o arriving transmissions from multiple users not aligned on chip boundaries unless users are perfectly synchronized, Produce self-jamming

  • Near-far problem

o signals closer to the receiver are received with less attenuation than signals  farther away

  • Soft handoff

o requires that the mobile acquires the new cell before it relinquishes the old; this is  more complex than hard handoff used in FDMA and TDMA schemes

  • Air-interface is the most complex

 

Question No

Trunking System concept and description? 10

Trunking

► Allows a large number of users to share a small number of channels

► Channel allocated per call basis from a pool of available channels

► Relies on statistical behavior of users so that a fixed number of channels (circuits) may accommodate a large random user community

► Trunking theory is used to determine number of channels for particular area (users)

► Tradeoff between the number of available channels and likelihood of call blocking during peak calling hours

Trunking Theory

► Developed by Erlang, Danish Mathematician, how a large population can be accommodated by a limited number of servers, in late 19th century

► Today, used to measure traffic intensity

► 1 Erlang represents the amount of traffic intensity carried by a completely occupied channel

i.e. one call-hour per hour or one call-minute per minute

0.5 Erlang: Radio channel occupied 30 minutes during 1 hour

 

Q 52: Which QoS classes are defined in WiMAX? Write the possible application and their related parameters to specify QoS. QoS Category Applications QoS Specifications
UGS Unsolicited Grant Service VoIP  Maximum Sustained Rate

 Maximum Latency Tolerance

 Jitter Tolerance

rtPS Real-Time Polling Service Streaming Audio or Video  Minimum Reserved Rate

 Maximum Sustained Rate

 Maximum Latency Tolerance

 Traffic Priority

ErtPS Extended Real-Time Polling Service Voice with Activity Detection (VoIP)  Minimum Reserved Rate

 Maximum Sustained Rate

 Maximum Latency Tolerance

 Jitter Tolerance

 Traffic Priority

nrtPS Non Real-Time Polling Service File Transfer Protocol (FTP)  Minimum Reserved Rate

 Maximum Sustained Rate

 Traffic Priority

BE Best-Effort Service Data Transfer, Web Browsing, etc.  Maximum Sustained Rate

 Traffic Priority

 

Question No

QoS of GPRS BEARER

4 parameters:

  1. Service precedence

 3 classes

  1. Reliability parameter

 3 classes

  1. Delay parameters

 4 classes

  1. Throughput parameter

 Maximum and mean bit rates

 

QoS profile is included in Packet Data Protocol (PDP) context

Negotiation managed through PDP procedures (activation, modification and deactivation)

 

Question No

QOS multimedia UMTS 10 MARKS

Based on the QoS criteria, multimedia services has been further classified

Conversational

The most delay sensitive, e.g. applications video telephony, VoIP

Streaming

Flow which is steady and continuous, it is server to user

Interactive

Web browsing is an example. A user may request timetables of buses, trains or flight schedule

Background

Short messages, file transfer, email that has least stringent requirements of QoS

 

 What is reed Solomon codes and how it works

Subclass of nonbinary BCH codes

Data processed in chunks of m bits, called symbols

An (n, k) RS code has parameters:

Symbol length: m bits per symbol

Block length: n = 2m – 1 symbols = m(2m – 1) bits

Data length: k symbols

Size of check code: n k = 2t symbols = m(2t) bits

Minimum distance: dmin = 2t + 1 symbols

 

Question No

List GPRS Channels and Describe Logical Channels

Physical Channels

  • Defined by timeslot (0-7) and radio frequency channel
  • Shared Basic Physical Sub Channel
  • Dedicated Basic Physical Sub Channel
  • Packet Data Channel (PDCH)

o Control

o User data

Logical Channels

  • Mapped by the MAC to physical channels
  • Control channels for control, synchronization and signaling
  • Packet Traffic channels

 

Question No

Explain IS-95 reverse link?

IS-95 or cdmaOne

Supports up to 64 users that are orthogonally coded

Channel bandwidth is 1.25 MHz

Widely deployed in N. America, Korea, Japan, China, S. America, Australia

Channel data rate is 1.2288 Mchips/s (Mega Chips)

 

Question No

 Why min rate of call is different from from traffic intensity?

Grade of Service:

GOS is a benchmark used to define performance of a particular trunked system

Measure of the ability of a user to access trunked system during the busiest hour.

Busy hour is based on the demands in an hour during a week, month or year.

Typically occur during rush hours between 4 pm to 6 pm.

GOS is typically given as likelihood of call blocking or delay experienced greater

than certain queue time

Traffic Intensity:

Traffic intensity is measured as call request rate multiplied by call holding time

User traffic intensity of Au Erlang is

(1) Au= λH

Note that traffic is not necessarily the carried traffic but offered to the trunked system

If offered load increases the system capacity, the carried traffic becomes limited

In Erlang, max possible carried traffic is the number of channels C AMPS is designed for a GOS of 2% blocking i.e. 2 out of 100 calls will be blocked due to channel occupancy

There are two types of commonly used trunked systems

Blocked Calls Cleared:

User is given immediate request if a channel is available.

If no channel available, the requesting user is blocked and free to try later

Assume call arrivals as Poisson Distribution

the Erlang B formula determines the probability that call is blocked with no queuing,

is a measure of GOS for trunked system

Blocked Calls Delayed:

Queue is provided to hold blocked calls.

Call request may be delayed until a channel becomes available

Its measure of GOS is defined as the probability that a call is blocked after waiting specific length of time in the queue

The likelihood of a call not having immediate access is determined by Erlang C formula

 

Question No

Cs718 8 a.m today spring 2018

Bluetooth connection diagram master clave mode 15

 

Q: Briefly describe Mac sub layer. 5

  • It is responsible for mapping logical channels to the transport channels
  • It provides an interface between L1 & L3 and provides packet multiplexing / de-multiplexing
  • It performs measurement related to traffic volume on logical channels and reporting to layer 3

 

Q: What is the limit on number of nodes in a piconet? 5

A piconet can contain maximum 255 nodes in an in-active low power state.

 

  1. 3 Difference between MANET and wireless mesh network. 5

MANET: mobile ad hoc network (MANET), also known as wireless ad hoc network or ad hoc wireless network, is a continuously self-configuring, infrastructure-less network of mobile devices connected wirelessly.

Each device in a MANET is free to move independently in any direction, and will therefore change its links to other devices frequently. Each must forward traffic unrelated to its own use, and therefore be a router.

wireless mesh network (WMN) is a communications network made up of radio nodes organized in a mesh topology. It is also a form of wireless ad hoc network.

mesh refers to rich interconnection among devices or nodes. Wireless mesh networks often consist of mesh clients, mesh routers and gateways. Mobility of nodes is less frequent. If nodes constantly or frequently move, the mesh spends more time updating routes than delivering data.

 

Q.4. Difference between WCDMA and CDMA 2000 10 Marks

  1. CDMA is a 2G technology while WCDMA is a 3G technology
  2. CDMA and WCDMA are not used together
  3. WCDMA offers much faster speeds compared to CDMA
  4. CDMA uses frequency bands 1.25Mhz wide while WCDMA uses frequency bands 5Mhz wide
  5. The WCDMA doesn’t share the same design as CDMA
  6. CDMA and its successors are being phased out in favor of GSM and WCDMA

 

What is ZigBee Alliance?

 An organization with a mission to define reliable, cost effective, low-power, wirelessly networked, monitoring and control products based on an open global standard

 The alliance provides interoperability, certification testing, and branding.

 

Draw typical wireless sensor network communication architecture.

 

Q: Give different types of IEEE 802.15.4 devices, and also list the kind of functionalities the devices can perform. 5

There are two different device types:

  • A full function device (FFD)
  • A reduced function device (RFD)
  • The FFD can operate in three modes serving
    • Device
    • Coordinator
    • PAN coordinator
  • The RFD can only operate in a mode serving:
    • Device

 

Elaborate the Routing Challenges and Design Issues in Wireless Sensor Networks (WSN).

 

CS718 Final Term 09-09-2018

2).TDMA and connect MAC protocols in WSN.

3). Issues in Mobile IP

 

 

My paper 718 at 5 pm 9-9-18

2-TCP creates fluctuation n shrinkage to windows, why?

5-name 03 sesor actuator network

6-piconet

i- starting piconet

ii- child piconet

 

Q6:Mobile IP was intended to work with legacy correspondent hosts and legacy applications.  However, some advantages may be gained if correspondent hosts are aware of mobility in certain ways.

If a correspondent host is able to do IP-in-IP decapsulation, it may be able to communicate more efficiently with the mobile host despite the presence of ingress filtering.  Why?

If a correspondent host is able to maintain a mapping between a mobile host’s local IP address and its home IP address, and receive updates to that mapping from the mobile host, it may be able to communicate more efficiently with the mobile host than is possible with standard Mobile IP.  Why?

CS 718 WN Paper

Q: What are 802.16 burst types and downlink services?  5

Burst profiles

 Each burst profile has mandatory exit threshold and minimum entry threshold

 SS allowed to request a less robust DIUC once above the minimum entry level

 SS must request fall back to more robust DIUC once at mandatory exit threshold

 Requests to change DIUC done with DBPC-REQ or RNG-REQ messages

 

Downlink transmissions

 Two kinds of bursts: TDM and TDMA

 All bursts are identified by a DIUC: Downlink Interval Usage Code

 TDMA bursts have resync preamble: Allows for more flexible scheduling

 Each burst may contain data for several terminals

 SS must recognize the PDUs with known CIDs

 DL-MAP message signals downlink usage

  1. No.5: WSN 3 MAC , 4 Routing and 3 transport protocol types. 10
  2. No.7: By diagram show interspacing SIFS, PISF, DIFS and AIFS 10

 Host inter-frame space (SIFS): The SIFS is used for the highest-priority transmissions, such as RTS/CTS frames and positive acknowledgments

 PCF interframe space (PIFS): The PIFS is used by the PCF during contention-free operation. Stations with data to transmit in the contention-free period can transmit after the PIFS has elapsed and pre-empt any contention-based traffic

 DCF interframe space (DIFS): The DIFS is the minimum medium idle time for contention-based services. Stations may have immediate access to the medium if it has been free for a period longer than the DIFS.

 Extended interframe space (EIFS): The EIFS is not a fixed interval. It is used only when there is an error in frame transmission.

 

  1. No.9: Message distribution in ESS 10

Two services involved in distribution of messages within DS.

Distribution

 Primary service used to exchange MAC frames between stations of two

 Source sends to AP of one BSS, which sends to DS. DS then sends destination.

 Message transport in DS is beyond the scope of IEEE 802.11 standard.

Integration

 Enables transfer of a data between a station on an IEEE 802.11 LAN integrated IEEE 802.x LAN (Wired LAN).

 It takes care of any address translation and media conversion logic

 

CS-718 Final Term 2015                  Date 30-03-15 at 2PM

What are the characteristic of ad-hoc and future challenges? (10)

Characteristics:

Heterogeneous nodes

Self-creating

► not rely on a pre-existing fixed infrastructure

Self-organizing

► no predetermined topology

Self-administering

► no central control

creating a network “on the fly”

 

Challenges:

  1. Spectrum allocation
  2. Self-configuration
  3. Medium access control (MAC)
  4. Energy efficiency
  5. TCP Performance
  6. Mobility management
  7. Security & privacy
  8. Routing protocols
  9. Multicasting
  10. QoS
  11. Service Location, Provision, Access

 

Question No.9. (15 points) (From lecture 40)

Give IEEE 802.15.3 superframe format and discuss its parts superframe # in detail with its format?

  1. 1 ending procedure of pick net

 

Q: Explain the factors effecting reliability in WSN. 10

Following are the factors which affect the reliability of WSN:-

Node Heterogeneity:

o Heterogeneous nodes with different roles & capabilities

o Diverse modalities

o If cluster heads may have more energy & computational capability, they take care of transmissions to the base station (BS)

 

 Fault tolerance

o Some sensors may fail due to lack of power, physical damage, or environmental interference

o Adjust transmission power, change sensing rate, reroute packets through regions with more power

 Network dynamics

o Mobile nodes

o Mobile events, e.g., target tracking

o If WSN is to sense a fixed event, networks can work in a reactive manner

 A lot of applications require periodic reporting

 Transmission media

o Wireless channel

o Limited bandwidth: 1 – 100Kbps

o MAC

 Contention-free, e.g., TDMA or CDMA

 Contention-based, e.g., CSMA, MACA, or 802.11

 Connectivity

Some sensors may die after consuming their battery power

o Connectivity depends on possibly random deployment

 Coverage

o An individual sensor’s view is limited

o Area coverage is an important design factor

 Data aggregation

 

Interframe Spacing
• Short interframe space (SIFS) üThe SIFS is used for the highest-priority transmissions, such as RTS/CTS frames and positive acknowledgments. • PCF interframe space (PIFS) üThe PIFS is used by the PCF during contention-free operation. Stations with data to
transmit in the contention-free period can transmit after the PIFS has elapsed and preempt any contention-based traffic
• DCF interframe space (DIFS) üThe DIFS is the minimum medium idle time for contention-based services. Stations may
have immediate access to the medium if it has been free for a period longer than the DIFS.
• Extended interframe space (EIFS) üThe EIFS is not a fixed interval. It is used only when there is an error in frame transmission

Introduction to WSNs
• A sensor network is composed of a large number of sensor nodes, which are densely deployed
either inside the phenomenon or very close to it.
• Features:
üRandom deployment
üSelf-organizing
üCooperative capabilities
üLocal computation

Multi-radio Unification Protocol
• Discovering neighbours.
üAfter the discovering procedures, neighbours are classified into MUP enabled and legacy
nodes.
• Selecting a NIC
üBased on one-hop round trip time (RTT) measurements. MUP selects the NIC with the

shortest RTT between a node and its neighbors.
• Utilizing the selected NIC for a long period.
üThis period is determined by a random process and in the order of 10–20 s.
• Switching channels.
üAfter the random time period, all NICs are measured again through one-hop probe
messages. If an NIC has a certain amount of quality improvement than the existing NIC,
then it is selected for sending packets.

 

Mobility Management
• Location Management: enables system to track location of mobile terminal (MT)
üLocation updates and paging
• Handoff Management: the process by which an MT keeps its connection when it moves from
one point of attachment (base station or access point) to another

 

In order to support mobility, Mobile IP includes three capabilities:
1. Discovery
o Mobile Agents send ICMP router advertisements with mobility agent
advertisement extension periodically informing mobile nodes of its presence.
o Mobile node is responsible for the discovery process.
o In order to receive an advertisement, the mobile node may optionally request
one from an agent or simply wait for the next advertisement.
2. Registration
o Mobile node recognizes that it is on a foreign network, acquires a Care-ofAddress and requests its home agent to forward its data packets to the foreign
agent.
o The process of registration requires 4 steps:
i. Mobile node request forwarding service by sending registration request
to the foreign agent.
ii. Foreign agent relays this request to the home agent.
iii. Home agent accepts or denies the request and sends registration reply
to the foreign agent.
iv. Foreign agent relays this reply to Mobile node.
3. Tunneling
o After registration, an IP tunnel is set up between the home agent and care-ofaddress of the mobile node.
o Home agent broadcasts gratuitous ARP request which causes all nodes in the subnet to update their ARP caches to map the mobile nodes IP address to the
home agents link level address.
o Thus home agent receives packets destined to the mobile node, and forwards
the packets to the foreign agent through the IP tunnel.
o In the foreign network, decapsulation is done by the foreign agent or by the
mobile node itself.
o A correspondent node assumes that the reply from the mobile node is coming
from its home network and continues to send the packet to the home agent.

 

Access and Privacy Services IEEE802
• Authentication
üEstablishes the identity of stations.
üHowever, IEEE 802.11 requires mutually acceptable, successful authentication before
association.
• De-authentication
üInvoked to terminate existing authentication
• Privacy
üStandard provides optional use of encryption to assure privacy

 

Q 42: 8032.15.3 channel time division.

Channel time management

There are three methods for communicating data between DEVs in the piconet: 1. Sending asynchronous data in the CAP, if present. 2. Allocating channel time for isochronous streams in the CTAP. 3. Allocating asynchronous channel time in the CTAP.

Dynamic channel selection

 Due to ISM bands, piconet is subject to interference from unlicensed users or other 802.15.3 piconets

 PNC has the capability to dynamically change the channel that the piconet is using without requiring either user intervention or the disruption of services in the piconet.

 To evaluate the status of the current channel as well as other channels, the PNC is able to use many methods including:

  1. Gathering information about the current channel from other DEVs in the piconet using the Channel Status Request command. 2. Performing a passive scan of the channels. 3. Requesting other DEVs to perform a channel scan using the Remote Scan Request command,

 

IEEE 802.16 Overview
• Family of standards for wireless metropolitan area networks (WMAN)
• Provide broadband (i.e., voice, data, video) connectivity
• Specifies the air interface, including the medium access control (MAC) layer and multiple
physical layer specifications
• 802.16e is an amendment to 802.16d (fixed or nomadic wireless broadband) to support mobility
üVehicular speeds up to 75 mph

 

T-MAC: Choosing TA
• Requirement: a node should not sleep while its neighbors are communicating, potential next
receiver
• TA > C+R+T
üC – contention interval length;
üR – RTS packet length;
üT – turn-around time, time bet. end of RTS and start of CTS;
• TA = 1.5 * (C+R+T);
• Pros
üPerforms better under variable traffic load
• Cons
üHigher overheads than SMAC to maintain variable wakeup schedule.
üUnfairness and unpredictable delay.

 

TCP Slow Start
• Sender calculates a congestion window for a receiver
• Start with a congestion window size equal to one segment
• Exponential increase of the congestion window up to the congestion threshold, then linear
increase
• Missing acknowledgement causes the reduction of the congestion threshold to one half of the
current congestion window
• Congestion window starts again with one segment

 

Bluetooth protocols
• Service Discovery Protocol (SDP)
üDefines a service record format
o Information about services provided by attributes
o Attributes composed of an ID (name) and a value
o IDs may be universally unique identifiers (UUIDs)

  • Defines an inquiry/response protocol for discovering services
    üSearching for and browsing services
    • RFCOMM (based on GSM TS07.10)
    üEmulates a serial-port to support a large base of legacy (serial-port-based) applications
    üAllows multiple ports over a single physical channel between two devices
    • Telephony Control Protocol Spec (TCS)
    üCall control (setup & release)
    üGroup management for gateway serving multiple devices
    • Legacy protocol reuse
    üReuse existing protocols

 

Q6:Mobile IP was intended to work with legacy correspondent hosts and legacy applications.  However, some advantages may be gained if correspondent hosts are aware of mobility in certain ways.

If a correspondent host is able to do IP-in-IP decapsulation, it may be able to communicate more efficiently with the mobile host despite the presence of ingress filtering.  Why?

If a correspondent host is able to maintain a mapping between a mobile host’s local IP address and its home IP address, and receive updates to that mapping from the mobile host, it may be able to communicate more efficiently with the mobile host than is possible with standard Mobile IP.  Why?

 

  1. IEEE 802.11 Protocols Differences:

IEEE 802.11a: PHY Standard: 8 channels: 54 Mbps: 5 GHz band: OFDM.

IEEE 802.11b: PHY Standard: 3 channels: 11 Mbps: 2.4 GHz band: FHSS, DSSS.

IEEE 802.11d: MAC Standard: operate in variable power levels:

IEEE 802.11e: MAC Standard: QoS support: EDCF.

IEEE 802.11f: Inter-Access Point Protocol: 2nd half 2002

IEEE 802.11h: Supplementary MAC Standard: Enhanced version of 802.11a to support European Regulatory provides TPC and DFS.

IEEE 802.11i: Supplementary MAC Standard: Alternative WEP

IEEE 802.11n: 100 + Mbps: Enhancement to 802.11g using MIMO

IEEE 802.11s: mesh networking extension

 

Differentiate between core specification and profile specification in Bluetooth.

Bluetooth Standards Documents

  • Core specifications

 Details of various layers of Bluetooth protocol architecture

 Bluetooth is a layered protocol architecture

Core protocols

Cable replacement and telephony control protocols

Adopted protocols

  • Profile specifications

 Use of Bluetooth technology to support various applications

 

Categorize and discuss the basic types of traffic data access in WCDMA. 10

There are four basic types of traffic classes

  • Conversational class
    • real-time connection, performed between human users, really low delay, nearly symmetric, e.g., speech
  • Streaming class -> real-time connection, transferring data as a steady and continuous, low delay, asymmetric, e.g., video
  • Interactive class -> non-real-time packet data, response requested from other end-user, reasonable round-trip delay, e.g., Web browsing
  • Background class -> non-real-time packet data, no immediate action expected, less sensitive to delivery time, e.g. e-mail

 

Mobile IP was intended to work with legacy correspondent hosts and legacy applications.  However, some advantages may be gained if correspondent hosts are aware of mobility in certain ways.

 

If a correspondent host is able to do IP-in-IP decapsulation, it may be able to communicate more efficiently with the mobile host despite the presence of ingress filtering.  Why?

 

If a correspondent host is able to maintain a mapping between a mobile host’s local IP address and its home IP address, and receive updates to that mapping from the mobile host, it may be able to communicate more efficiently with the mobile host than is possible with standard Mobile IP.  Why?

 

WSN 3 MAC , 4 Routing and 3 transport protocol types.            10

 

Give IEEE 802.15.3 superframe format and discuss its parts superframe # in detail with its format?

 

Given network A, B, C that are connected to the Internet. A client of C starts communication with client of A. during session client of A moves to network B. explain with diagrams the given scenario and how will it possible to maintain session while all the three network A, B, and C are connected to the Internet. Explain with diagrams and label entitles? (10)

 

architectural diagram of WSN

 

Mobile IP was intended to work with legacy correspondent hosts and legacy applications. However, some advantages may be gained if correspondent hosts are aware of mobility in certain ways.

 

If a correspondent host is able to do IP-in-IP decapsulation, it may be able to communicate more efficiently with the mobile host despite the presence of ingress filtering. Why?

 

If a correspondent host is able to maintain a mapping between a mobile host’s local IP address and its home IP address, and receive updates to that mapping from the mobile host, it may be able to communicate more efficiently with the mobile host than is possible with standard Mobile IP. Why?

 

Why we cannot use CSMA/CD in Wireless LAN and under what conditions it can be used? 5

 

If a DSSS-based cellular system had poor or inadequate power regulation, what effect will be noticeable in the network?

 

Differentiate between Intra-PCF and Inter-PCF in CDMA2000. 5

 

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