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DHANALAKSHMI SRINIVASAN ENGINEERING COLLEGE
PERAMBALUR-
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING
EC6802-WIRELESS NETWORKS UNIT I
- State the significance of radio transmission over infrared(Apr/May 17) Infrared light transmission is one of the important technologies used in wireless LAN. It is based on the transmission of infrared light at 900 nm wavelength.Infrared technology uses diffuse light reflected at walls, furniture etc. Or directed light when line of sight (LOS) exists between sender and receiver.
- List out the applications of WLAN. Transfer of medical images Remote access to patient records Remote monitoring of patients Remote diagnosis of patients at home or in an ambulance In telemedicine Surveillance Internet supporting database.
- What is IEEE 802.11? The IEEE 802.11 is the first WLAN standard that has secured the market in large extent. The primary goal of the standard was the specification of a simple and robust that offers time bounded and asynchronous services.
4.Give any two requirements of HIPERLAN. Nov/Dec 2015) Data rates of 23.529 Mbps Multi-hop and Ad-hoc networking Support of time bounded services
5.What are the three phases in channel access in HIPERLAN-1? Prioritization phase Contention phase Transmission phase
6.What is meant by BRAN? The BRAN (Broadband Radio Access Networks (BRAN) is standardized by the EuropeanTelecommunications Standards Institute (ETSI). Primary motivation of BRAN is the deregulationand privatization of the telecommunication sector. BRAN technology is independent from theprotocols of the fixed network. BRAN can be used for ATM and TCP/IP networks.
7.What is Bluetooth? Nov/Dec 2015) Bluetooth is an inexpensive personal area Ad-hoc network operating in unlicensed bands and owned by the user. It is an open specification for short range wireless voice and data communications that was developed for cable replacement in PAN (Personal Area Network).
8.What is WIMAX? WIMAX is the air interface for the actual radio interface network, where both fixed and mobilcan have access to the network. Its specification is IEEE 802.16.
9.What are the frequency bands of IEEE 802.16? The 802.16 standard defines a number of air interfaces that can be divided into, 10-66 GHz licensed band Below 11 GHz licensed bands Below 11 GHZ unlicensed bands
- What is the need for WATM? WATM systems had to be designed for transferring voice, classical data, video, multimedia etc.
PART B 1.Explain the architecture and reference model of HIPERLAN- 2 in detail(Nov/Dec2014) (Apr/May 2014) (Nov/Dec2015) (Apr/May 2015 )
HIPERLAN/2 has a very high transmission rate up to 54 Mbit/s. This is achieved by making use of a modularization method called Orthogonal Frequency Digital Multiplexing (OFDM). OFDM is particularly efficient in time-dispersive environments, i.e. where the radio signals are reflected from many points
HIPERLAN/2 connections are time-division multiplexed and connection-oriented, either bidirectional point-to-point or unidirectional point-to-multipoint connections. There is also a dedicated broadcast channel through which the traffic from an AP reaches all terminals.
Physical Layer
The channeling is implemented by Orthogonal Frequency Division Multiplexing (OFDM) due to its excellent performance on highly dispersive channels. The basic idea of OFDM is to transmit broadband, high data rate information by dividing the data into several interleaved, parallel bit streams, and let each bit stream modulate a separate subcarrier. The channel spacing is 20 MHz, which allows high bit rates per channel yet has reasonable number of channels: 52 subcarriers are used per channel (48 subcarriers for data, 4 subcarriers tracking the phase for coherent demodulation). The independent frequency subchannels are used for one transmission link between the AP and the MTs
Data Link Control Layer
The Data Link Control (DLC) layer includes functions for both medium access and transmission (user plane) as well as terminal/user and connection handling (controlplane)
. It consists of the following sublayers :
Medium Access Control (MAC) protocol Error Control (EC) protocol (or Logical Link Control, LLC ) Radio Link Control (RLC) protocol (also known as RCP) with the associated signalling entities: o DLC Connection Control
an alternative to cable and DSL".IEEE 802.16m or Wireless MAN-Advanced was a candidate for the 4G, in competition with the LTE Advanced standard.
Features: High data rates Quality of service Scalability Security Mobility WiMAX physical layer WiMAX Media access control Spectrum Allocation for WiMAX
**3.Explain any two MAC mechanism used in IEEE 802.11 WLAN systems. (Nov/Dec
- (Apr/May 2015)**
Mechanisms Mandatory basic method based on a version of CSMA/CA An option method avoiding the hidden terminal problem A contention free polling method for time –bounded service Priorities SIFS-Short Inter frame Spacing PIFS-PCF Inter frame Spacing DIFS-DCF Inter frame Spacing
he IEEE 802.16 MAC was designed for point-to-multipoint broadband wireless access applications. The primary task of the WiMAX MAC layer is to provide an interface between the higher transport layers and the physical layer.
The MAC layer takes packets from the upper layer, these packets are called MAC service data units (MSDUs) and organizes them into MAC protocol data units (MPDUs) for transmission over the air. For received transmissions, the MAC layer does the reverse.
The IEEE 802.16-2004 and IEEE 802.16e-2005 MAC design includes a convergence sublayer that can interface with a variety of higher-layer protocols, such as ATM TDM Voice, Ethernet, IP, and any unknown future protocol.
The 802.16 MAC is designed for point-to-multipoint (PMP) applications and is based on collision sense multiple access with collision avoidance (CSMA/CA).
The MAC incorporates several features suitable for a broad range of applications at different mobility rates, such as the following −
Privacy key management (PKM) for MAC layer security. PKM version 2 incorporates support for extensible authentication protocol (EAP). Broadcast and multicast support. Manageability primitives. High-speed handover and mobility management primitives. Three power management levels, normal operation, sleep, and idle. Header suppression, packing and fragmentation for an efficient use of spectrum. Five service classes, unsolicited grant service (UGS), real-time polling service (rtPS), non-real-time polling service (nrtPS), best effort (BE), and Extended real-time variable rate (ERT-VR) service.
4. Explain about WATM in detail
Wireless ATM (WATM; sometimes also called wireless, mobile ATM, wmATM) specifies
a complete communication system (Acampora, 1996), (Ayanoglu, 1996).
While many aspects of the IEEE WLANs originate from the data communication
community, many WATM aspects come from the telecommunication industry.
Two main subgroups Radio Access Layer Mobile ATM Radio Access Layer Radio Resource Control Wireless Media Access Wireless Data Link Control Handover issues Location management : WATM networks must be able to locate a wireless terminal or a mobile user. Mobile routing: Each time a user moves to a new access point, the system must reroute traffic. Handover signalling: The network must provide mechanisms which search for new access points, set up new connections and signal the actual change of the access point. QoS and traffic control: WATM should be able to offer many QoS parameters. The network must pay attention to the incoming traffic (and check if it conforms to some traffic contract) in a similar way to today’s ATM (policing). Network management: All extensions of protocols or other mechanisms also require an extension of the management functions to control the network. ensure wireless access, the working group discussed the following topics belonging to a radio access layer (RAL):
Radio resource control: Radio frequencies, modulation schemes, antennas,
channel coding etc. have to be determined.
Wireless media access: Different media access schemes are possible, each with
specific strengths and weaknesses for, e.g., multi-media or voice applications.
time-sharing the process. To do so it must use the associated master’s address and proper clock offset.
PROTOCOL STACK
Core specification Profile specification
6.Explain in detail about the significance of BRAN.
Broadband radio Access Network is standardized by ETSI
TYPES
BRAN has specified four different network types: HIPERLAN 1: This high-speed WLAN supports mobility at data rates above 20 Mbit/s. Range is 50 m, connections are multi-point-to-multi-point using ad-hoc or infrastructure networks. HIPERLAN/2: This technology can be used for wireless access to ATM or IP networks and supports up to 25 Mbit/s user data rate in a point-to-multi-point configuration. Transmission range is 50 m. HIPERACCESS: This technology an alternative to cable modems or Xdsl technologies. Transmission range is up to 5 km, data rates of up to 25 Mbit/s are supported. HIPERLINK: To connect different HIPERLAN access points or HIPERACCESS nodes with a high-speed link, HIPERLINK technology can be chosen. HIPERLINK provides a fixed point-to-point connection with up to 155 Mbit/s. Currently, there are no plans regarding this standard. Common characteristics of HIPERLAN/2, HIPERACCESS, and HIPERLINK include their support of the ATM service classes CBR, VBR-rt, VBR-nrt, UBR, and ABR.
This technology fulfills the requirements of ATM QoS support, mobility, wireless access, and high bandwidth. As an access network, BRAN technology is independent from the protocols of the fixed network. BRAN can be used for ATM and TCP/IP networks as illustrated in Fig Based on possibly different physical layers, the DLC layer of BRAN offers a common interface to higher layers. To cover special characteristics of wireless links and to adapt directly to different higher layer network technologies, BRAN provides a network convergence sublayer. This is the layer which can be used by a wireless ATM network, Ethernet, Firewire, or an IP network.
Layered model of BRAN wireless access networks
7. Explain in detail about spread spectrum techniques.
Spread-spectrum telecommunications is a signal structuring technique that employs direct sequence, frequency hopping, or a hybrid of these, which can be used for multiple access and/or multiple functions. This technique decreases the potential interference to other receivers while achieving privacy. Spread spectrum generally makes use of a sequential noise-like signal structure to spread the normally narrowband information signal over a relatively wideband (radio) band of frequencies. The receiver correlates the received signals to retrieve the original information signal. Originally there were two motivations: either to resist enemy efforts to jam the communications (anti-jam, or AJ), or to hide the fact that communication was even taking place, sometimes called low probability of intercept (LPI) or low probability of detection (LPD). Although spread spectrum methods have been used for many years to establish LPD communication, the fundamental limits of covert communications were only recently studied [1]^ and extended for many scenarios, such as artificial noise generation [2].
Frequency-hopping spread spectrum (FHSS), direct-sequence spread spectrum (DSSS), time-hopping spread spectrum (THSS), chirp spread spectrum (CSS), and combinations of these techniques are forms of spread spectrum. Each of these techniques employs pseudorandom number sequences—created using pseudorandom number generators—to determine and control the spreading pattern of the signal across the allocated bandwidth. Wireless standard IEEE 802.11 uses either FHSS or DSSS in its radio interface.
5.What is SIP?
The Session Initiation Protocol (SIP) is an application-layer control (signaling) protocol for
creating, modifying and terminating sessions with one or more participants. It is a IETF
(Internet Standard) RFC 3261 protocol.
6.What are the characteristics of MANET? (Nov/Dec 16) The characteristics of MANET are Dynamic Topologies Bandwidth Constraints and Variable Capacity Links Energy Constrained Operations Limited Physical Security
7.What are the challenging issues in ad hoc network maintenance(May/June 12) The challenging issues in ad hoc network are Medium access scheme Routing Multicast routing Transport layer protocol Pricing Schemes
8.Why are ad hoc networks needed? (May/June 12) Ad hoc networking is often needed where an infrastructure network cannot be deployed and managed. The presence of dynamic and adaptive routing protocols enables quick formation of ad hoc networks and is suitable for emergency situations like natural disasters, spontaneous meetings or military conflicts.
- What is DSDV? Distance-Vector Routing (DSDV) is a table driven routing scheme for ad-hoc mobile networks. The main contribution of the algorithm was to solve the routing loop problem.
10.List the Source-initiated On-Demand Routing Protocols. Ad-hoc On-Demand Distance Vector Routing (AODV) Dynamic Source Routing (DSR) Temporarily Ordered Routing Algorithm (TORA) Associatively Based Routing (ABR) Signal Stability Based Routing (SSR)
PART B
1.State the entities and terminologies used in mobile IP (Apr/may 17)
Mobile IP The following gives an overall view of Mobile IP, and the extensions needed for the internet to support the mobility of hosts. The following material requires some familiarity with Internet protocols, especially IP. A very good overview which includes detailed descriptions of classical Internet protocols is given in Stevens (1994). Many new approaches related to Internet protocols,applications, and architectures can be found in Kurose (2003).
ENTITIES AND TERMINOLOGY
Mobile Node Correspondent node Home network Foreign network Foreign agent Care of Address Home Agent
Mobile node (MN):
A mobile node is an end-system or router that can change its point of attachment to the internet using mobile IP. The MN keeps its IP address and can continuously communicate with any
Correspondent node (CN): At least one partner is needed for communication. In the following the CN represents this partner for the MN. The CN can be a fixed or mobile node. Home network: The home network is the subnet the MN belongs to with respect to its IP address. No mobile IP support is needed within the home network Foreign network: The foreign network is the current subnet the MN visitsand which is not the home network. Foreign agent (FA): The FA can provide several services to the MN during its visit to the foreign network. The
FA can have the COA (defined below),the MN. The FA can be they belong to the foreign
network as opposed to the MN which is only visiting. For mobile IP functioning, FAs are not
necessarily needed. Typically, an FA is implemented on a router for the subnet the MN
attaches to.
A tunnel establishes a virtual pipe for data packets between a tunnel entry and a tunnel endpoint. Packets entering a tunnel are forwarded inside the tunnel and leave the tunnel unchanged. Tunneling, i.e., sending a packet through a tunnel, is achieved by using encapsulation.
IP-within-IP encapsulation (see Figure 2.1.5): The entire IP datagram becomes the payload in a new IP datagram. The inner, original IP header is unchanged except to decrement time-to-live (TTL) by 1. The outer header is a full
Fig 2.1.5 IP within IP encapsulation
IP header in which: Two fields, version number and type of service, are copied from an inner header The source address typically is the IP address of the home agent, and the destination address is the CoA for the intended destination.
Minimal encapsulation This results in less overhead and can be used if the mobile node, home agent, and foreign agent all agree to do so. A new header with the following fields is used between the original IP header and the original IP payload: Protocol, Header checksum, Original destination address, Original source address The following fields in the original IP header are modified to form the new outer IP header: Total length Protocol Header checksum Source address Destination address.
The encapsulation (home agent) prepares the encapsulated datagram which is now suitable for tunneling and delivery across the Internet to the care the minimal forwarding header are restored to the original IP header and the forwa header is removed from the datagram.
The total length field in the IP header is decremented by the size of the minimal forwarding
header and the checksum field is recomputed
4.Explain in detail, the IPV6 & DHCP
Today’s Internet operates over the common network layer datagram protocol, Internet Protocol version 4 (IPv4). In the early 1990s, a new design of addressing scheme was initiated within the Internet Engineering Task Force (IETF weaknesses of IPv4. The result was IPv6 (see Figure 2.3.2). The single most significant advantage IPv6 offers is increased destination and source addresses.
The encapsulation (home agent) prepares the encapsulated datagram which is now suitable for tunneling and delivery across the Internet to the care-of address. The fields in the minimal forwarding header are restored to the original IP header and the forwa header is removed from the datagram.
Fig 2.1.6 Minimal encapsulation
The total length field in the IP header is decremented by the size of the minimal forwarding
header and the checksum field is recomputed
in detail, the IPV6 & DHCP
Today’s Internet operates over the common network layer datagram protocol, Internet Protocol version 4 (IPv4). In the early 1990s, a new design of addressing scheme was initiated within the Internet Engineering Task Force (IETF) due to the recognized weaknesses of IPv4. The result was IPv6 (see Figure 2.3.2). The single most significant advantage IPv6 offers is increased destination and source addresses.
The encapsulation (home agent) prepares the encapsulated datagram which is now of address. The fields in the minimal forwarding header are restored to the original IP header and the forwarding
The total length field in the IP header is decremented by the size of the minimal forwarding
Today’s Internet operates over the common network layer datagram protocol, Internet Protocol version 4 (IPv4). In the early 1990s, a new design of addressing scheme was ) due to the recognized weaknesses of IPv4. The result was IPv6 (see Figure 2.3.2). The single most significant
5.Explain in detail, the Session Initiation Protocol (SIP)
SIP is used for provisioning services in IP-based mobile networks. SIP specifications define an architecture of user agents and servers (proxy server, redirect server, register) that support communications between SIP peers through user tracking, call routing, and so on. In SIP, each user is uniquely identified by an SIP universal resource indicator, which is used as the identifier to address the called user when the sending session initiation requests. However, an IP address is associated with the user in order to route SIP signaling from the SIP register. A SIP user registers with the SIP register to indicate its presence in the network and its willingness to receive incoming session initiation requests from other users. A typical session in SIP begins with a user sending an INVITE message to a peer through SIP proxies. When the recipient accepts the request and the initiator is notified, the actual data flow begins, usually taking a path other than the one taken by the SIP signaling messages.
INTERNET REFERENCE MODEL:
Although many useful protocols have been developed in the context of OSI, the overall 7-layer model has not flourished. The TCP/IP architecture has come to dominate. There are a number of reasons for this outcome. The most important is that the key TCP/IP protocols were mature and well tested at a time when similar OSI protocols were in the development stage.
Fig 2.1.7 Internet Reference Mode
6.Explain in detail, the registration process in mobile IP.
When the mobile node receives an agent advertisement, the mobile node registers through the foreign agent, even when the mobile node might be able to acquire its own co- located care-of address. This feature enables sites to restrict access to mobility services. Through agent advertisements, mobile nodes detect when they have moved from one subnet to another.
Mobile IP registration provides a flexible mechanism for mobile nodes to communicate their current reachability information to their home agent. The registration process enables mobile nodes to perform the following tasks:
Request forwarding services when visiting a foreign network Inform their home agent of their current care-of address Renew a registration that is due to expire Deregister when they return home Request a reverse tunnel
Registration messages exchange information between a mobile node, a foreign agent, and the home agent. Registration creates or modifies a mobility binding at the home agent, associating the mobile node's home address with its care-of address for the specified lifetime.
The registration process also enables mobile nodes to: Register with multiple foreign agents Deregister specific care-of addresses while retaining other mobility bindings Discover the address of a home agent if the mobile node is not configured with this information
Registration request
Home address Home agent COA Identification
Registration reply
UDP packet Type Code
7. Explain in detail, agent discovery process in mobile IP. One initial problem of an MN after moving is how to find a foreign agent. How does the MN discover that it has moved? For this purpose mobile IP describes two methods: agent advertisement and agent solicitation, which are in fact router discovery methods plus extensions.
These advertisement messages can be seen as a beacon broadcast into the subnet. For these advertisements Internet control message protocol (ICMP) messages according to RFC 1256 (Deering,1991) are used with some mobility extensions. The agent advertisement packet according to RFC 1256 with the extension for mobility is shown in Figure 2.1.3 The upper part represents the ICMP packet while the lower part is the extension needed for mobility.
Home agent IP address An identification field Registration lifetime Remaining lifetime of pending or current registration.
Fig 2.1.4 Agent discovery procedure
8.Explain with an example DSR
Dynamic source routing (DSR) , therefore, divides the task of routing into two separate problems (Johnson, 1996), (Johnson, 2002a):
● Route discovery: A node only tries to discover a route to a destination if it has to send something to this destination and there is currently no known route.
● Route maintenance: If a node is continuously sending packets via a route, it has to make sure that the route is held upright. As soon as a node detects problems with the current route, it has to find an alternative. The basic principle of source routing is also used in fixed networks, e.g. token rings. Dynamic source routing eliminates all periodic routing updates and works as follows. If a node needs to discover a route, it broadcasts a route request with a unique identifier and the destination address as parameters. Any node that receives a route request does the following.
If the node has already received the request (which is identified using the unique identifier), it drops the request packet.
● If the node recognizes its own address as the destination, the request has reached its target. ● Otherwise, the node appends its own address to a list of traversed hops in the packet and broadcasts this updated route request. UNIT III
1.What are the advantages and disadvantages of I – TCP? (Apr/may 17) Advantages: I-TCP does not require any changes in the TCP Protocol Transmission errors on the wireless link cannot propagate into the fixed network. Optimizing new mechanisms is quite simple because they only cover one single hop. Disadvantages: The loss of the end-to-end semantics of TCP might cause problems if the foreign agent partitioning the connection crashes.
2.What are the advantages of Mobile TCP? (Apr/may 17)
M-TCP maintains the TCP end-to-end semantics. The Supervisory Host (SH) does not send any ACK itself but forwards the ACKS from the MH. If the MH is detached, it avoids useless transmissions, slow starts or breaking connections by simply shrinking the sender’s window to zero. 3.What is Snooping TCP? The main drawback of I-TCP is the segmentation of the single TCP connection into two TCP connections, which losses the original end-to-end TCP semantics. A new enhancement which leaves the TCP intact and is completely transparent, is Snooping TCP. The main function is to buffer data close to the mobile hast to perform fast local retransmission in the case of packet loss.
4.What is time-out freezing? The MAC layer informs the TCP layer about an upcoming loss of connection or that the current interruption is not caused by congestion. TCP then stops sending and freezes the current state of its congestion window and further timers. When the MAC layer notices the upcoming interruption early enough, both the mobile and correspondent host can be informed.
5.What is Selective Retransmission? TCP acknowledgements are collective. They acknowledge in-order receipt of packets upto certain packets. Even if a single packet is lost, the sender has to retransmit everything starting from the lost packet. To overcome this problem, TCP can indirectly request a selective retransmission of packets. The receiver may acknowledge single packets and also trains of in-sequence packets.
6.What are the techniques for classical improvements?
