IEEE 802.16
Wireless 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
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Topics
 Introduction
 Physical Layer
 MAC Layer
(Medium Access Control)
 References
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Introduction
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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
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Legacy voice systems
Voice over IP
TCP/IP
Applications with different QoS requirements.
Main advantage :
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fast deployment, dynamic sharing of radio resources and low cost
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4
Architecture
Source: D. Miorandi Create Net
Uplink: direction from SS to BS
Downlink: direction from BS to SS
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IEEE 802.16 Extension
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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
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802.16b
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Improvement and fixes for 802.16a
802.16e
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Represents a 10 to 66GHz system profile
802.16d
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Increase spectrum to 5 and 6GHz
Provide QoS (for real-time voice and video service)
802.16c
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Support lower frequency 2 to 11Ghz both licensed and license-exempt
So reach more customers with less expensive
Lower data rates
Support Mesh-Network
Addresses on Mobile
Enable high-speed signal handoffs necessary for communications with users
moving at vehicular speeds
Focus on 802.16.1
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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
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Physical layer
 10-66GHz line of sight propagation. US use 20-25MHz, EU use
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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
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Time Division Duplexing (TDD)
Uplink and downlink share a channel but do not transmit simultaneously
Source: D. Miorandi Create Net
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Frequency Division Duplexing (FDD)
 Uplink and downlink operate on separate channels sometime
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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)
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Media Acces Control (MAC)
 Supports many different physical layer specifications, both
licensed and unlicensed.
 Connection orienteded
 Connection ID (CID)
 Channel access:
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UL-MAP
 Defines uplink channel access
 Defines uplink data burst profiles
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DL-MAP
 Defines downlink data burst profiles
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UL-MAP and DL-MAP are both transmitted in the beginning of
each downlink subframe (FDD and TDD).
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FDD Downlink subframe
Source: D. Miorandi Create Net
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Uplink subframe
Source: D. Miorandi Create Net
Grant bandwidth to specific SSs
SSs transmit in assigned allocation using burst profiles UIUC in UL-MAP
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MAC sublayers
 Service Specific Convergence Sublayer
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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
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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.
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used to distinguish between multiple uplink channels associated with the same
downlink channel
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many higher-layer sessions may share same CID (with same service parameters)
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Used in MAC PDU
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Common Part Sublayer
 SS enter network is assigned 3 management
connections
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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
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MAC PDU format
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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.
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MAC PDU header
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Transmission of MAC PDUs
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Transmission Convergence sublayer is between MAC and PHY
Transformation of variable length MAC PDUs into fixed length FEC block
MAC Message
MAC PDUs PDU1
Burst
P
Preamble
SDU 1
PDU2
FEC1
PDU3
PDU4
SDU2
PDU5
FEC2
FEC3
FEC blocks
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MAC Management Messages (rules)
 Handle initial ranging, negotiation, SS authentication and registration,
and describing downlink and uplink
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link describing:
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BS transmits channel uplink and downlink descriptor messages (UCD
and DCD) at periodic intervals
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UCD and DCD contain burst profile: info on modulation, errorcorrection, preamble length, etc.
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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
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determines power and burst profile changes (starts with lowest power
level and then moves up)
Create - net
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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
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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:
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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
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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 station’s
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
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Bandwidth allocate by Unicast Polling
BS
SS
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.
Poll(UL-MAP)
Request
Alloc(UL-MAP)
Data
Source: D. Miorandi Create Net
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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:
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If the response indicates corrections, the SS makes these corrections
and sends another ranging request.
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If the response indicates success, the SS is ready to send data on the
UL.
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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 SS’s
public key.
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Registration and IP connectivity
 Registration
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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
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After registration SS attains an IP address via DHCP and establishes time of
day via Internet Time Protocol
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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)
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Questions ?
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