IEEE 802.16 Wireless MAN (Wireless Metropolitan Network)

1
IEEE 802.16Wireless MAN(Wireless Metropolitan
Network)

• A Technical Overview of the WirelessMANTM Air
  Interface for Broadband Wireless Access, Carl
  Eklund, Roger B. Marks, Kenneth L. Stanwood and
  Stanley Wang June 2002
• Presented by Phuong Nguyen
• For 681 Advanced Computer Network Fall 2007

2
Topics

• Introduction
• Physical Layer
• MAC Layer (Medium Access Control)
• References

3
Introduction

• Goal Provide high-speed Internet access to home
  and business subscribers, without wires.
• Base stations (BS) can handle thousands of
  subscriber stations (SS)
• BS can control all data traffic goes between BS
  and SS through the allocation of bandwidth on the
  radio channel.
• 802.16 is a Bandwidth on Demand system
• Access control prevents collisions.
• Supports
• Legacy voice systems
• Voice over IP
• TCP/IP
• Applications with different QoS requirements.
• Main advantage
• fast deployment, dynamic sharing of radio
  resources and low cost

4
(No Transcript)
5
Architecture
Source D. Miorandi Create Net
Uplink direction from SS to BS Downlink
direction from BS to SS
6
IEEE 802.16 Extension

• 802.16 standard was approved in 2001
• 802.16.1 (10-66 GHz, line-of-sight, up to
  134Mbit/s)
• 802.16.2 (minimizing interference between
  coexisting WMANs.)
• 802.16a
• Support lower frequency 2 to 11Ghz both licensed
  and license-exempt
• So reach more customers with less expensive
• Lower data rates
• Support Mesh-Network
• 802.16b
• Increase spectrum to 5 and 6GHz
• Provide QoS (for real-time voice and video
  service)
• 802.16c
• Represents a 10 to 66GHz system profile
• 802.16d
• Improvement and fixes for 802.16a
• 802.16e
• Addresses on Mobile
• Enable high-speed signal handoffs necessary for
  communications with users moving at vehicular
  speeds
• Focus on 802.16.1

7
SAP Service Access Point PDU Protocol Data Unit
System access, bandwidth allocation connection
establishment, connection maintenance
Accept, perform classification, process higher
PDUs Deliver CS PDU to MAC SAP Receive CS PDUs
from the peer entity
Authentication, security key exchange, encryption
Multiple specifications each appropriate to
frequency range (ex 802.16.1 10-66GHz up to
134Mbit/s) and application
IEEE Std 802.16 protocol layering, showing SAPs
8
Physical layer

• 10-66GHz line of sight propagation. US use
  20-25MHz, EU use 28MHz
• Point to multipoint BS transmit a TDM (Time
  Division Multiplexing) signal with individual SSs
  allocated time slots serially
• Access the uplink by time division multiple
  access (TDMA)
• Burst single-carrier modulation
• Allows use of directional antennas
• Allows use of two different duplexing schemes
• Frequency Division Duplexing (FDD)
• Time Division Duplexing (TDD)
• Support for both full and half duplex stations

9
Time Division Duplexing (TDD)
Uplink and downlink share a channel but do not
transmit simultaneously
Source D. Miorandi Create Net
10
Frequency Division Duplexing (FDD)

• Uplink and downlink operate on separate channels
  sometime simultaneously
• Support full duplex SSs which can transmit and
  receive simultaneously
• Half duplex which do not
• Adaptive Data Burst Profiles
• Transmission parameters (e.g. modulation and FEC
  settings) can be modified on a frame-by-frame
  basis for each SS.
• Profiles are identified by Interval Usage Code
  (DIUC and UIUC)
• Using both
• TDM (Time Division Multiplexing) and
• TDMA (Time Division Multiple Access)

11
Media Acces Control (MAC)

• Supports many different physical layer
  specifications, both licensed and unlicensed.
• Connection orienteded
• Connection ID (CID)
• Channel access
• UL-MAP
• Defines uplink channel access
• Defines uplink data burst profiles
• DL-MAP
• Defines downlink data burst profiles
• UL-MAP and DL-MAP are both transmitted in the
  beginning of each downlink subframe (FDD and TDD).

12
FDD Downlink subframe
Source D. Miorandi Create Net
13
Uplink subframe
Grant bandwidth to specific SSs SSs transmit in
assigned allocation using burst profiles UIUC in
UL-MAP
Source D. Miorandi Create Net
14
MAC sublayers

• Service Specific Convergence Sublayer
• ATM CS defined for ATM service
• Packet CS defined for IPv4, IPv6, Ethernet
• Classify service data unit SDUs to proper MAC
  connection, preserve or enable QoS and enable
  bandwidth allocation

15
Common Part Sublayer

• Point to multi point
• Request bandwidth, associate QoS, transport and
  routing data
• SS has universal 48bit MAC address. BS has 48-bit
  Base Station ID (not MAC address)
• Connections identified by 16-bit CID.
• used to distinguish between multiple uplink
  channels associated with the same downlink
  channel
• many higher-layer sessions may share same CID
  (with same service parameters)
• Used in MAC PDU

16
Common Part Sublayer

• SS enter network is assigned 3 management
  connections
• Basic connection transfer short critical MAC
  messages
• Primary connection transfer longer more delay
  torelent messages (authentication, connection
  setup)
• Secondary connection transfer of standard base
  management messages such as DHCP, TFTP, SNMP
• In addition, transport connection for contracted
  services
• Other additional connections
• Contention based initial access
• Broadcast transmissions for Downlink, polling of
  SSs if needed
• Additional connections for multicast

17
MAC PDU format

• MAC PDU Formats
• -The MAC PDU (protocol data unit) is the data
  unit exchanged between the MAC layers of the BS
  and its SSs.
• -Consists of a fixed-length MAC header, a
  variable-length payload, and an optional cyclic
  redundancy check (CRC).
• MAC Header Formats
• Two MAC header formats The first is the
  generic MAC header that begins each MAC PDU
  containing either MAC management messages or CS
  data. The second is the bandwidth request header
  used to request additional bandwidth.

18
MAC PDU header
19
Transmission of MAC PDUs

• Transmission Convergence sublayer is between MAC
  and PHY
• Transformation of variable length MAC PDUs into
  fixed length FEC block

20
MAC Management Messages (rules)

• Handle initial ranging, negotiation, SS
  authentication and registration, and describing
  downlink and uplink
• link describing
• BS transmits channel uplink and downlink
  descriptor messages (UCD and DCD) at periodic
  intervals
• UCD and DCD contain burst profile info on
  modulation, error-correction, preamble length,
  etc.
• uplink and downlink map messages (UL-MAP, DL-MAP)
  define burst start times and allocate access to
  corresponding link channel
• ranging subscriber stations transmit ranging
  requests at initialization and then periodically
• determines power and burst profile changes
  (starts with lowest power level and then moves up)

Create - net
21
MAC Management Messages

• Uplink schedule service
• Unsolicited Grant Service (UGS)
• Real-Time Polling Service (rtPS)
• Non-Real-Time Polling Service (nrtPS)
• Best Effort Service
• Bandwidth request and grants
• SS authentication and registration

22
Bandwidth request and allocation

• SSs may request bw in 3 ways
• Use the contention request opportunities
  interval upon being polled by the BS (multicast
  or broadcast poll).
• Send a standalone MAC message called BW request
  in an allready granted slot.
• Piggyback a BW request message on a data packet.
• BS grants/allocates bandwidth in one of two
  modes
• Grant Per Subscriber Station (GPSS)
• Grant Per Connection (GPC)
• Decision based on requested bw and QoS
  requirements vs available resources.
• Grants are realized through the UL-MAP.

Source D. Miorandi Create Net
23
Approaches to Bandwidth Grant

• Two basic approaches on the way to grant BW
• 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 connections agreements
• Suitable for many connections per terminal
  off-loading base stations work
• Allows more sophisticated reaction to QoS needs
• Low overhead but requires intelligent subscriber
  station
• Bandwidth Grant per Connection (GPC)
• Base station grants bandwidth to a connection
• Mostly suitable for few users per subscriber
  station
• Higher overhead, but allows simpler subscriber

24
Bandwidth allocate by Unicast Polling

1. BS allocates space for the SS in the uplink
   subframe.
2. SS uses the allocated space to send a bw request.
3. BS allocates the requested space for the SS (if
   available).
4. SS uses allocated space to send data.

BS
SS
Poll(UL-MAP)
Request
Alloc(UL-MAP)
Data
Source D. Miorandi Create Net
25
Initial Ranging

• Upon learning what parameters to use for its
  Initial ranging, SS scanning for UL_MAP messages
  present in every frame
• SS will send the burst using minimum power
  setting and try again if it does not get response
  
• BS command timing advance and power adjustment to
  SS based on SS request. Also provide SS with
  basic and primary management CIDs
• SS receive response
• If the response indicates corrections, the SS
  makes these corrections and sends another ranging
  request.
• If the response indicates success, the SS is
  ready to send data on the UL.

26
Negotiation Capabilities and Authentication

• Negotiation Capabilities
• After successful completion of initial ranging,
  the SS sends a capability request message to the
  BS describing its capabilities in terms of the
  supported modulation levels, coding schemes and
  rates, and duplexing methods.
• The BS accepts or denies the SS, based on its
  capabilities.
• Authentication
• After negotiation, the BS authenticates the SS
  and provides key material to enable the ciphering
  of data.
• The SS sends the X.509 digital certificate and
  certificate of manufacturer and a description of
  the supported cryptographic algorithms to its BS.
  
• The BS validates the identity of the SS,
  determines the cipher algorithm and protocol that
  should be used, and sends an Authentication Reply
  contain Authorization Key encrypted with SSs
  public key.

27
Registration and IP connectivity

• Registration
• SS will register the network after successful
  completion of authentication
• It sends a registration request message to the
  BS, and the BS sends a registration response to
  the SS.
• The registration exchange includes
• IP version support
• SS managed or non-managed support
• ARQ parameters support
• Classification option support
• CRC support
• Flow Control
• IP connectivity
• After registration SS attains an IP address via
  DHCP and establishes time of day via Internet
  Time Protocol

28
References

• IEEE Standard 802.16 A technique overview of the
  WirelessMANTM Air Interface for Broachband
  Wireless Access, Carl Eklund, Roger B. Marks,
  Kenneth L. Stanwood and Stanley Wang, June 2002.
• IEEE std 802.16 standard 2004 part 16 (895 pages)

29

• Questions ?