This document provides an overview of wireless LAN and Bluetooth technologies. It describes IEEE 802.11 standards for wireless LAN including the basic service set, extended service set, infrastructure and ad-hoc modes. It covers the physical layers, MAC protocols and services of 802.11. It also summarizes ATM and its extension to wireless networks, issues in the transition, proposed W-ATM architectures, advantages and disadvantages. Finally it defines Bluetooth technology, the protocol stack and unlicensed frequency band used.

1. UNIT I
WIRELESS LAN

3. Single Cell Wireless LAN Configuration

4. Multi-Cell Wireless LAN Configuration

5. IEEE 802.11
Wireless connection within 100m range
This standard defines:
1.Medium Access Control (MAC) sub layer
2. MAC management protocols and services
3.Three Physical layer for wireless connectivity – fixed,
portable and moving devices

6. System architecture
1. Infrastructure based network
2. Ad-hoc network

7. Infrastructure based:

8. IEEE 802.11 - BSS
 MAC protocol and physical medium specification for
wireless LANs
 Smallest building block is basic service set (BSS)
 Number of stations
 Same MAC protocol
 Competing for access to same shared wireless medium
 May be isolated or connect to backbone distribution
system (DS) through access point (AP)
 AP functions as bridge
 DS can be switch, wired network, or wireless network

9. BSS Configuration
 Simplest: each station belongs to single BSS
 Within range only of other stations within BSS
 Can have two BSSs overlap
 Station could participate in more than one BSS
 Association between station and BSS dynamic
 Stations may turn off, come within range, and go out of
range

10. Extended Service Set (ESS)
 Two or more BSS interconnected by DS
 Typically, DS is wired backbone but can be any network
 Appears as single logical LAN to LLC

11. Access Point (AP)
 Logic within station that provides access to DS
 Provides DS services in addition to acting as station
 To integrate IEEE 802.11 architecture with wired LAN,
portal used
 Portal logic implemented in device that is part of
wired LAN and attached to DS
 E.g. Bridge or router

12. Services
Service Provider Category
Association Distribution system MSDU delivery
Authentication Station LAN access and
security
Deauthentication Station LAN access and
security
Dissassociation Distribution system MSDU delivery
Distribution Distribution system MSDU delivery
Integration Distribution system MSDU delivery
MSDU delivery Station MSDU delivery
Privacy Station LAN access and
security
Reassocation Distribution system MSDU delivery

13. Ad-Hoc based: iBSS

14. IEEE 802.11 Protocol Architecture

15. scenario of IEEE 802.11 wireless LAN connected to a
switched IEEE 802.3 Ethernet via a bridge

16. Distributed Coordination Function
 DCF sublayer uses CSMA
 If station has frame to transmit, it listens to medium
 If medium idle, station may transmit
 Otherwise must wait until current transmission complete
 No collision detection
 Not practical on wireless network
 Dynamic range of signals very large
 Transmitting station cannot distinguish incoming weak signals
from noise and effects of own transmission
 DCF includes delays
 Amounts to priority scheme
 Interframe space

17. Point Coordination Function (PCF)
 Alternative access method implemented on top of DCF
 Polling by centralized polling master (point coordinator)
 Uses PIFS when issuing polls
 PIFS smaller than DIFS
 Can seize medium and lock out all asynchronous traffic while it issues polls
and receives responses
 E.g. wireless network configured so number of stations with time-
sensitive traffic controlled by point coordinator
 Remaining traffic contends for access using CSMA
 Point coordinator polls in round-robin to stations configured for
polling
 When poll issued, polled station may respond using SIFS
 If point coordinator receives response, it issues another poll using PIFS
 If no response during expected turnaround time, coordinator issues
poll

18. 802.11 Physical Layer
 Subdivided into two
1. PLCP – Physical layer Convergence protocol - provides Clear Channel
Assessment (CCA) and PHY service access point (SAP)
2. PMD-Physical Medium Dependent – Modulation and
encoding/decoding

19. Original 802.11 Physical Layer -
FHSS
 Frequency-hopping spread spectrum
 2.4 GHz ISM band at 1 Mbps and 2 Mbps
 Uses multiple channels
 Signal hopping from one channel to another based on a pseudonoise sequence
 1-MHz channels are used
 23 channels in Japan
 70 in USA
 Hopping scheme adjustable
 E.g. Minimum hop rate forUSA is 2.5 hops per second
 Minimum hop distance 6 MHz in North America and most of Europe and 5
MHz in Japan
 Two-level Gaussian FSK modulation for 1-Mbps
 Bits encoded as deviations from current carrier frequency
 For 2 Mbps, four-level GFSK used
 Four different deviations from center frequency define four 2-bit combinations

20. 1. SFD – Start Frame Delimiter
2. PLW- PLCP length word
3. PSF-PLCP Signaling Field
4. HEC- Header Error Check

21. Original 802.11 Physical Layer -
DSSS
 Three physical media
 Direct-sequence spread spectrum
 2.4 GHz ISM band at 1 Mbps and 2 Mbps
 Up to seven channels, each 1 Mbps or 2 Mbps, can be
used
 Depends on bandwidth allocated by various national
regulations
 13 in most European countries
 One in Japan
 Each channel bandwidth 5 MHz
 Encoding scheme DBPSK for 1-Mbps and DQPSK for 2-
Mbps

23. Original 802.11 Physical Layer –
Infrared
 Omnidirectional
 Range up to 20 m
 1 Mbps used 16-PPM (pulse position modulation)
 Each group of 4 data bits mapped into one of 16-PPM symbols
 Each symbol a string of 16 bits
 Each 16-bit string consists of fifteen 0s and one binary 1
 For 2-Mbps, each group of 2 data bits is mapped into one of
four 4-bit sequences
 Each sequence consists of three 0s and one binary 1
 Intensity modulation
 Presence of signal corresponds to 1

24. Original 802.11 MAC Layer

29.  RTS - READY TO SEND
 CTS - CLEAR TO SEND
 NAV - Network Allocation Vector

31. 802.11a
 5-GHz band
 Uses orthogonal frequency division multiplexing (OFDM)
 Not spread spectrum
 Also called multicarrier modulation
 Multiple carrier signals at different frequencies
 Some bits on each channel
 Similar to FDM but all subchannels dedicated to single source
 Data rates 6, 9, 12, 18, 24, 36, 48, and 54 Mbps
 Up to 52 subcarriers modulated using BPSK, QPSK, 16-QAM, or
64-QAM
 Depending on rate
 Subcarrier frequency spacing 0.3125 MHz
 Convolutional code at rate of 1/2, 2/3, or 3/4 provides forward error
correction

32. 802.11b
 Extension of 802.11 DS-SS scheme
 5.5 and 11 Mbps
 Chipping rate 11 MHz
 Same as original DS-SS scheme
 Same occupied bandwidth
 Complementary code keying (CCK) modulation to achieve higher
data rate in same bandwidth at same chipping rate
 CCK modulation complex
 Overview on next slide
 Input data treated in blocks of 8 bits at 1.375 MHz
 8 bits/symbol  1.375 MHz = 11 Mbps
 Six of these bits mapped into one of 64 code sequences
 Output of mapping, plus two additional bits, forms input to QPSK
modulator

33. 11-Mbps CCK Modulation Scheme

35. What is ATM?
Asynchronous Transfer Mode (ATM)
 A networking technology developed by the telephone
companies to handle all types of data using fixed 53-
byte cells, or packets.
 Creates virtual point-to-point circuit connections
between the source and the destination.
 Data rates from 25 to 622 Mbps.

36. What is ATM?
• The small cell size
allows ATM to transmit
video, audio, and
computer data over the
same network, while
guaranteeing a preset
QoS level for each.

37. The Promise of W-ATM
 Extension of LAN for mobile user
 Simplified wiring and configuration
 Provide high-speed data access for users without need
for a new wired infrastructure
 Create unforeseen opportunities for future
applications

38. W-ATM

39. Transition Issues
 Physical Layer
 Infrared vs. Radio
 Circuit-switched vs. Packet-switched
 Channel Coding
 Multiple Antennas
 Operating Frequency
 Licensed vs. Unlicensed Frequency

40. Transition Issues
 Data Link Layer
 Encapsulation
 Header Compression
 ARQ (Automatic Repeat Request) vs. FEC (Forward
Error Correction)
 Quality-of-Service Issues
 Split Functionality
 An Example Protocol

41. Proposed Architecture

42. Advantages of W-ATM
 Benefits of ATM made mobile
 Free to roam
 Flexible bandwidth allocation
 Efficient multiplexing of traffic
 Availability of existent ATM switching
 Flexibility of reusing same frequency
 Soft handoff without any data loss

43. Disadvantages of W-ATM
 Delay to multi-path interference
 Hop-by-hop routing method not adequate
 Virtual connection takes longer
 Poor physical level characteristics
 High noise interference
 Finding a suitable wireless channel

45. What is Bluetooth?
Bluetooth is a high-speed, low-power microwave
wireless link technology, designed to connect phones,
laptops, PDAs and other portable equipment together
with little or no work by the user. Bluetooth
technology allows users to make ad hoc wireless
connections between devices like mobile phones,
desktop or notebook computers without any cable.
Devices carrying Bluetooth-enabled chips can easily
transfer data at a speed of about 1 Mbps in basic mode
within a 50m range or beyond through walls, clothing
and even luggage bags.

47. BLUETOOTH PROTOCOL
 Bluetooth uses the unlicensed 2.4 GHz ISM (Industrial Scientific
and Medical) frequency band. There are 79 available Bluetooth
channels spaced 1 MHz apart from 2.402 GHz to 2.480 GHz. The
Bluetooth standard is managed and maintained by Bluetooth
Special Interest Group. IEEE has also adapted Bluetooth as the
802.15.1a standard. Bluetooth allows power levels starting from
1mW covering 10cm to 100mW covering up to 100 meters. These
power levels are suitable for short device zone to personal area
network within a home.
 Bluetooth supports both unicast (point-to-point) and multicast
(point-to-multipoint) connections. Bluetooth protocol uses the
concept of master and slave. In a master slave protocol a device
cannot talk as and when they desire. They need to wait till the
time the master allows them to talk.

49. BLUETOOTH PROTOCOL STACK
Different applications may run over different protocol
stacks. Nevertheless, each one of these different
protocol stacks use a common Bluetooth data link and
physical layer. Not all applications make use of all the
protocols. Instead, applications run over one or more
vertical slices from this protocol stack. Typically,
additional vertical slices are for services supportive of
the main application, like TCS Binary (Telephony
Control Specification), or SDP (Service Discovery
Protocol).

50. Bluetooth protocol stack can be divided into four basic
layers according to their functions.
1. Baseband,
2. Link Manager Protocol (LMP),
3. Logical Link Control and Adaption Protocol
(L2CAP),
4. Service Discovery Protocol (SDP).

51. 1. Baseband
The Baseband and Link Control Layer enable the physical
RF link between Bluetooth units forming a piconet. This
layer uses inquiry and paging procedures to synchronize
the transmission with different Bluetooth devices. Using
SCO (Synchronous Connection Oriented) and ACL
(Asynchronous Connection Less) links, different packets
can be multiplexed over the same RF link. ACL packets are
used for data only, while the SCO packet can contain audio
only or a combination of audio and data. All audio and data
packets can be provided with different levels of CRC (Cyclic
Redundancy Code) or FEC (Forward Error Correction) for
error detection or correction.

52. 2. Link Manager Protocol (LMP)
When two Bluetooth devices come within each other’s
radio range, link managers of either device discover
each other. LMP then engages itself in peer- to-peer
message exchange. These messages perform various
security functions starting from authentication to
encryption. LMP layer performs generation and
exchange of encryption keys as well. This layer
performs the link setup and negotiation of baseband
packet size. LMP also controls the power modes,
connection state and duty cycles of Bluetooth devices
in a piconet.

54. 3. Logical Link Control and
Adaptation Protocol (L2CAP)
 This layer is responsible for segmentation of large
packets and the reassembly of the fragmented
packets.L2CAP is also responsible for multiplexing of
Bluetooth packets from different applications.

55. 4. Service Discovery Protocol
(SDP)
 The SDP enables a Bluetooth device to join a piconet.
Using SDP a device inquires what services are available
in a piconet and how to access them. SDP uses a client-
server model where the server has a list of services
defined through service records. One service record in
a server describes the characteristics of one service. In
a Bluetooth device, they can be only one SDP server. If
a device provides multiple services, one SDP server
acts on behalf of all of them.

56. Bluetooth Security
 In a wireless environment where every bit is on the air,
security concerns are high. Bluetooth offers security
infrastructure starting from authentication, key
exchange to encryption. In addition to encryption, a
frequency-hopping scheme with 1600 hops/sec is
employed. All of this makes the system difficult to
eavesdrop.

57. Bluetooth Security
 The main security features offered by Bluetooth include a
challenge response routine for authentication, a stream
cipher for encryption, and a session key generation. Each
connection may require a one-way, two-way, or no
authentication using the challenge- response routine. The
security algorithms use the public identity of a device, a
secret private user key, and an internally generated random
key as input parameters. For each transaction, a new
random number is generated on the Bluetooth chip. Key
management is left to higher layer software. The following
figure shows several steps in the security architecture of
Bluetooth.

59. The first step, called pairing, is necessary if two
Bluetooth devices have never met before. To set up
trust between the two devices a user can enter a secret
PIN into both devices. This PIN can have a length of
up to 16 byte. Based on the PIN, the device address,
and random numbers, several keys can be computed
which can be used as link key for authentication. The
authentication is a challenge-response process based
on the link key, a random number generated by a
verifier (the device that requests authentication), and
the device address of the claimat (the device that is
authenticated)

60. Based on the link key, and again a random number an
encryption key is generated during the encryption
stage of the security architecture. This key has a
maximum size of 128 bits and can be individually
generated for each transmission. Based on the
encryption key, the device address and the current
clock a payload key is generated for ciphering user
data. The payload key is a stream of pseudo-random
bits. The ciphering process is a simple XOR of the
user data and the payload key.

61. HIgh PErformance Radio
Local Area Networks
(HIPERLAN)

62. I. Introduction
 Roughly speaking there are two types of wireless
networks:
 Local Area Networks (LAN)
 Bluetooth, 802.11 Family, HiperLAN Family, HomeRF...
 Wide Area Networks (WAN)
 GSM, 3G, 4G, Iridium...

63. Mobility and data rates for communications standards

64.  Two main standards families for Wireless Lan:
 IEEE 802.11 (802.11b, 802.11a, 802.11g...)
 ETSI Hiperlan (Hiperlan Type 1, Type 2, HiperAccess,
HiperLink...)
 HiperLAN Family
Hiperlan 1 Hiperlan2 HiperAccess HiperLink
Description Wireless
Ethernet
Wireless ATM Wireless Local
Loop
Wireless Point-
to-Point
Freq. Range 5GHz 5GHz 5GHz 17GHz
PHY Bit Rate 23.5Mbps 6~54Mbps ~25Mbps
(data rate)
~155Mbps
(data rate)

65. Motivation of HiperLAN
 Massive Growth in wireless and mobile
communications
 Emergence of multimedia applications
 Demands for high-speed Internet access
 Deregulation of the telecommunications industry

66. The History, Present and Future
HiperLAN Type 1
Developed by ETSI during 1991 to 1996
Goal: to achieve higher data rate than IEEE 802.11 data rates:
1~2 Mbps, and to be used in ad hoc networking of portable
devices
Support asynchronous data transfer, carrier-sense multiple
access multiple access with collision avoidance (CSMA/CA), no
QoS guaranteed.
Products
Proxim's High Speed RangeLAN5 product family
(24Mbps; 5GHz; QoS guaranteed)
RadioLAN’s products for indoor wireless communication
(10Mbps; 5GHz; Peer-to-Peer Topology)

67. HiperLAN Type 2
Next generation of HiperLAN family: Proposed by ETSI BRAN
(Broadband Radio Access Networks) in 1999, and is still under
development.
Goal: Providing high-speed (raw bit rate ~54Mbps)
communications access to different broadband core networks
and moving terminals
Features: connection-oriented, QoS guaranteed, security
mechanism, highly flexibility
Product: Prototypes are available now, and commercial
products are expected at the end of 2001 (Ericsson).
HiperAccess and HiperLink
In parallel to developing the HIPERLAN Type 2 standards,
ETSI BRAN has started work on standards complementary to
HIPERLAN Type 2

68. Relevant Organizations
Standards body: ETSI (European Telecommunications Standards
Institute, www.etsi.org)
Technology alliance:
HiperLAN2 Global Forum (H2GF, www.hiperlan2.com): promote
HiperLAN Type 2 as a standard, in order to accelerate its use in
business and consumer industries.
OFDM Forum (www.ofdm-forum.com): OFDM is the cornerstone
technology for high-speed wireless LAN such as HiperLAN.
Industry backers: Texas Instruments, Dell, Bosch, Ericsson,
Nokia,Telia, Xircom…

69.  Typical application scenarios
 HiperLAN: A complement to present-day wireless
access systems, giving high data rates to end-users in
hot-spot areas.
 Typical app. Environment: Offices, homes, exhibition
halls, airports, train stations, etc.
 Different with Bluetooth, which is mainly used for
linking individual communication devices within the
personal area network

70. II. Hiperlan2 System Overview
 Features
 5 GHz technology, up to 54 Mbit/s
 Generic architecture supporting:
Ethernet, IEEE 1394, ATM, 3G etc
 Connection-oriented with QoS per conn.
 Security - authentication & encryption
 Plug-and-play radio network using DFS
 Optimal throughput scheme

71. MAC
CAC
PHY
HiperLAN Type 1 Reference Model
PHY
MAC
EC
ACF DCC
RLC
DLC
CL
HiperLAN Type 2 Reference Model
Control Plane User Plane
MAC: Medium Access Sublayer EC: Error Control
CAC: Channel Access Control Sublayer RLC: Radio Link Control
PHY: Physical Layer RRC: Radio Resource Control
DLC: Data Link Control Layer ACF: Association Control Function
CL: Convergence Layer DCC: DLC Connection Control
Architecture
RRC

72. Physical Layer
 Data units on physical layer: Burst of variable
length, consist of a preamble and a data field
Reference configuration
1: information bits
2: scrambled bits
3: encoded bits
4: interleaved bits
5: sub-carrier symbols
6: complex baseband OFDM symbols
7: PHY bursts

73. Spectrum plays a crucial role in the deployment of
WLAN
Currently, most WLAN products operate in the
unlicensed 2.4GHz band, which has several
limitations: 80MHz bandwidth; spread spectrum
technology; interference
Spectrum allocation for Hiperlan2

74. Modulation scheme: Orthogonal frequency-
division multiplexing (OFDM)
Robustness on highly dispersive channels of
multipath fading and intersymbol interference
Spectrally efficient
Admits great flexibility for different
modulation alternatives
Facilitated by the efficiency of FFT and IFFT
algorithms and DSP chips
Hiperlan2: 19 channels (20MHz apart). Each
channel divided into 52 subcarriers

75. Encoding: Involves the serial sequencing of data,
as well as FEC
Key feature: Flexible transmission modes
With different coding rates and modulation schemes
Modes are selected by link adaptation
BPSK, QPSK as well as 16QAM (64QAM) supported
Mode Modulation Code rate Physical layer bit
rate (Mbps)
1 BPSK ½ 6
2 BPSK ¾ 9
3 QPSK ½ 12
4 QPSK ¾ 18
5 16QAM 9/16 27
6 16QAM ¾ 36
7(optional) 64QAM ¾ 54

76. Data Link Control Layer

77.  Three main control functions
 Association control function (ACF): authentication, key
management, association, disassociation, encryption
 Radio resource control function (RRC): handover, dynamic
frequency selection, mobile terminal alive/absent, power
saving, power control
 DLC user connection control function (DCC): setup and
release of user connections, multicast and broadcast
 Connection-oriented
 After completing association, a mobile terminal may request
one or several DLC connections, with one unique DLC
address corresponding to each DLC connection, thus
providing different QoS for each connection

78.  DLC: MAC Sublayer
 Basic frame structure (one-sector antenna)

79.  BCH (broadcast channel): enables control of radio resources
 FCH (frequency channel): exact description of the allocation of
resources within the current MAC frame
 ACH (access feedback channel): conveys information on previous
attempts at random access
 Multibeam antennas (sectors) up to 8 beams supported
 A connection-oriented approach, QoS guaranteed

80.  Hiperlan implements QoS through time slots
 QoS parameters: bandwidth, bit error rate, latency, and jitter
 The original request by a MT to send data uses specific time
slots that are allocated for random access.
 AP grants access by allocating specific time slots for a
specific duration in transport channels. The MT then sends
data without interruption from other MT operating on that
frequency.
 A control channel provides feedback to the sender.

81.  DLC: Error Control
 Acknowledged mode: selective-repeat ARQ
 Repetition mode: typically used for broadcast
 Unacknowledged mode: unreliable, low latency
 DLC: other features
 Radio network functions: Dynamic frequency selection;
handover; link adaptation; multibeam antennas; power control
 QoS support: Appropriate error control mode selected;
Scheduling performed at MAC level; link adaptation; internal
functions (admission, congestion control, and dropping
mechanisms) for avoiding overload

82. III. Comparison with Peers
 Main competitor: IEEE 802.11 Family
 802.11b vs. HiperLAN Type 1
 802.11a vs. HiperLAN Type 2
 Pros
 High rate with QoS support: Suitable for data and multimedia
app.
 Security mechanism
 Flexibility: different fixed network support, link adaptation,
dynamic frequency selection…

83.  Cons
 High cost
 Tedious protocol specification
 Limited outdoor mobility
 No commercial products in market till now
802.11 802.11b 802.11a HiperLAN2
Spectrum (GHz) 2.4 2.4 5 5
Max PHY rate (Mbps) 2 11 54 54
Max data rate, layer 3 (Mbps) 1.2 5 32 32
MAC CS CSMA/CA Central resource
control/TDMA/TDD
Connectivity Conn.-less Conn.-less Conn.-less Conn.-oriented
Multicast Yes Yes Yes Yes
QoS PCF (Point Control
Function)
PCF PCF ATM/802.1p/RSVP/DiffSe
rv (full control)
Frequency selection Frequency-hopping or
DSSS
DSSS Single
carrier
Single carrier with
Dynamic Frequency
Selection
Authentication No No No NAI/IEEE address/X.509

84. 802.11 802.11b 802.11a HiperLAN2
Encryption 40-bit RC4 40-bit RC4 40-bit RC4 DES, 3DES
Handover support No No No To be specified by
H2GF
Fixed Network Support Ethernet Ethernet Ethernet Ethernet, IP, ATM,
UMTS, FireWire
(IEEE 1394), PPP
Management 802.11 MIB 802.11 MIB 802.11 MIB HiperLAN/2 MIB
Radio link quality control No No No Link adaptation

86. WiMAX is not Wi-Fi

87. Overview of IEEE 802.16

88. Sub-standards of IEEE 802.16
 IEEE 802.16.1 - Air interface for 10 to 66 GHz
 IEEE 802.16.2 - Coexistence of broadband wireless access systems
 IEEE 802.16.3 - Air interface for licensed frequencies, 2 to 11 GHz

89. Basics of IEEE 802.16
IEEE 802.16 standards are concerned with the air interface between a subscriber’s
transceiver station and a base transceiver station
 The Physical Layer
 MAC Layer
 Convergence Layer

90. IEEE 802.16 Protocol Architecture

91. Physical Layer
 Specifies the frequency band, the modulation scheme, error-correction
techniques, synchronization between transmitter and receiver, data rate and the
multiplexing structure
 Both TDD and FDD alternatives support adaptive burst profiles in which
modulation and coding options may be dynamically assigned on a burst-by-burst
basis
 Three physical layer for services: Wireless MAN-SC2, Wireless MAN-OFDM and
Wireless MAN-OFDMA

92. Medium Access Control Layer
 Designed for point-to-multipoint broadband wireless access
 Addresses the need for very high bit rates, both uplink (to the base station) and
downlink (from the base station)
 Services like multimedia and voice can run as 802.16 MAC is equipped to
accommodate both continuous and bursty traffic

93. Convergence Layer
 Provides functions specific to the service being provided
 Bearer services include digital audio/video multicast, digital telephony, ATM,
Internet access, wireless trunks in telephone networks and frame relay

94. Reference Network Model
 The IEEE 802.16e-2005 standard provides the air interface for WiMAX but
does not define the full end-to-end WiMAX network. The WiMAX Forum's
Network Working Group (NWG), is responsible for developing the end-to-
end network requirements, architecture, and protocols for WiMAX, using
IEEE 802.16e-2005 as the air interface.
 The WiMAX NWG has developed a network reference model to serve as an
architecture framework for WiMAX deployments and to ensure
interoperability among various WiMAX equipment and operators.
 The network reference model envisions a unified network architecture for
supporting fixed, nomadic, and mobile deployments and is based on an IP
service model.

95. Reference Network Model
 The overall network may be logically divided into three parts:
1. Mobile Stations (MS) used by the end user to access the network.
2. The access service network (ASN), which comprises one or more base
stations and one or more ASN gateways that form the radio access network
at the edge.
3. Connectivity service network (CSN), which provides IP connectivity
and all the IP core network functions.

96. Reference Network Model

97. Reference Network Model
 The network reference model developed by the WiMAX Forum NWG
defines a number of functional entities and interfaces between those entities.
Fig below shows some of the more important functional entities.
1) Base station (BS): The BS is responsible for providing the air interface to
the MS. Additional functions that may be part of the BS are micromobility
management functions, such as handoff triggering and tunnel establishment,
radio resource management, QoS policy enforcement, traffic classification,
DHCP (Dynamic Host Control Protocol) proxy, key management, session
management, and multicast group management.

98. Reference Network Model
2) Access service network gateway (ASN-GW): The ASN gateway typically
acts as a layer 2 traffic aggregation point within an ASN. Additional
functions that may be part of the ASN gateway include intra-ASN location
management and paging, radio resource management and admission
control, caching of subscriber profiles and encryption keys, AAA client
functionality, establishment and management of mobility tunnel with base
stations, QoS and policy enforcement, foreign agent functionality for mobile
IP, and routing to the selected CSN.

99. Reference Network Model
3) Connectivity service network (CSN): The CSN provides connectivity to
the Internet, ASP, other public networks, and corporate networks. The CSN
is owned by the NSP and includes AAA servers that support authentication
for the devices, users, and specific services. The CSN also provides per user
policy management of QoS and security. The CSN is also responsible for IP
address management, support for roaming between different NSPs, location
management between ASNs, and mobility and roaming between ASNs.