31-03-2010, 08:31 PM
WiMAX for Broadband Wireless Access
Presented By:
Karim M. El Defrawy
ICS
UCI-2005
Outline
What is WiMAX
802.16 Introduction
802.16 MAC Highlights
802.16 Reference Model
MAC Convergence Sub-Layer (CS)
MAC Common Part Sub-Layer (CPS)
MAC Privacy Sub-Layer (PS)
Questions
What is WiMAX?
Worldwide Interoperability for Microwave Access (WiMAX) is the common name associated to the IEEE 802.16a/REVd/e
standards.
These standards are issued by the IEEE 802.16 subgroup that originally covered the Wireless Local Loop technologies
with radio spectrum from 10 to 66 GHz.
IEEE 802.16 -- Introduction
IEEE 802.16 (2001)
Air Interface for Fixed Broadband Wireless Access System MAC and PHY Specifications for 10 “ 66 GHZ (LoS)
One PHY: Single Carrier
Connection-oriented, TDM/TDMA MAC, QoS, Privacy
IEEE 802.16a (January 2003)
Amendment to 802.16, MAC Modifications and Additional PHY Specifications for 2 “ 11 GHz (NLoS)
Three PHYs: OFDM, OFDMA, Single Carrier
Additional MAC functions: OFDM and OFDMA PHY support, Mesh topology support, ARQ
IEEE 802.16d (July 2004)
Combines both IEEE 802.16 and 802.16a
Some modifications to the MAC and PHY
IEEE 802.16e (2005?)
Amendment to 802.16-2004
MAC Modifications for limited mobility
IEEE 802.16 -- Introduction
IEEE 802.16 -- Introduction
IEEE 802.16 MAC -- Highlights
WirelessMAN: Point-to-Multipoint and optional mesh topology
Connection-oriented
Multiple Access: DL TDM & TDMA, UL TDMA;UL OFDMA & TDMA, DL OFDMA & TDMA (Optional)
PHY considerations that affect the MAC
Duplex: TDD, FDD, FDX FDD BS and SS, HDX FDD SS
Adaptive burst profiles (Modulation and FEC) on both DL and UL
Protocol-independent core (ATM, IP, Ethernet)
Flexible QoS offering (CBR, rt-VBR, nrt-VBR, BE)
Strong security support
Reference Model
Adaptive PHY
Adaptive Burst Profiles
Burst profile: Modulation and FEC
On DL, multiple SSs can associate the same DL burst
On UL, SS transmits in an given time slot with a specific burst
Dynamically assigned according to page link conditions
Burst by burst
Trade-off capacity vs. robustness in real time
Duplex Scheme Support
The duplex scheme is Usually specified by regulatory bodies, e.g., FCC
Time-Division Duplex (TDD)
Downlink & Uplink time share the same RF channel
Dynamic asymmetry
does not transmit & receive simultaneously (low cost)
Frequency-Division Duplex (FDD)
Downlink & Uplink on separate RF channels
Full Duplexing (FDX): can Tx and Rx simultaneously;
Half-duplexing (HDX) SSs supported (low cost)
IEEE 802.16 MAC “ OFDM PHY TDD Frame Structure
IEEE 802.16 MAC “ OFDM PHY FDD Frame Structure
FDD MAPs Time Relevance
IEEE 802.16 MAC addressing and Identifiers
SS has 48-bit IEEE MAC address
BS has 48-bit base station ID
Not a MAC address
24-bit operator indicator
16-bit connection ID (CID)
32-bit service flow ID (SFID)
16-bit security association ID (SAID)
IEEE 802.16 MAC “ Convergence Sub-Layer (CS)
ATM Convergence Sub-Layer:
Support for VP/VC switched connections
Support for end-to-end signaling of dynamically created connections
ATM header suppression
Full QoS support
Packet Convergence Sub-Layer:
Initial support for Ethernet, VLAN, IPv4, and IPv6
Payload header suppression
Full QoS support
IEEE 802.16 MAC -- CS “ Packet Convergence Sub-Layer
Functions:
Classification: mapping the higher layer PDUs (Protocol Data Units) into appropriate MAC connections
Payload header suppression (optional)
MAC SDU (Service Data Unit), i.e, CS PDU, formatting
IEEE 802.16 MAC -- CPS “ MAC PDU Format
IEEE 802.16 MAC -- CPS -- Three Types of MAC PDUs
Data MAC PDUs
HT = 0
Payloads are MAC SDUs/segments, i.e., data from upper layer (CS PDUs)
Transmitted on data connections
Management MAC PDUs
HT =0
Payloads are MAC management messages or IP packets encapsulated in MAC CS PDUs
Transmitted on management connections
BW Req. MAC PDUs
HT =1; and no payload, i.e., just a Header
IEEE 802.16 MAC -- CPS “ Data Packet Encapsulations
IEEE 802.16 MAC “ CPS -- MAC Management Connections
Each SS has 3 management connections in each direction:
Basic Connection:
short and time-urgent MAC management messages
MAC mgmt messages as MAC PDU payloads
Primary Management connection:
longer and more delay tolerant MAC mgmt messages
MAC mgmt messages as MAC PDU payloads
Secondary Management Connection:
Standard based mgmt messages, e.g., DHCP, SNMP, ¦etc
IP packets based CS PDU as MAC PDU payload
IEEE 802.16 MAC “ CPS “ MAC Management Messages
IEEE 802.16 MAC “ CPS “ MAC PDU Transmission
MAC PDUs are transmitted in PHY Bursts
The PHY burst can contain multiple FEC blocks
MAC PDUs may span FEC block boundaries
Concatenation
Packing
Segmentation
Sub-headers
IEEE 802.16 MAC “ CPS “ MAC PDU Concatenation
IEEE 802.16 MAC “ CPS “ MAC PDU Fragmentation
IEEE 802.16 MAC “ CPS “ MAC PDU Packing
IEEE 802.16 MAC “ CPS QoS
Three components of 802.16 QoS
Service flow QoS scheduling
Dynamic service establishment
Two-phase activation model (admit first, then activate)
Service Flow
A unidirectional MAC-layer transport service characterized by a set of QoS parameters, e.g., latency, jitter, and
throughput assurances
Identified by a 32-bit SFID (Service Flow ID)
Three types of service flows
Provisioned: controlled by network management system
Admitted: the required resources reserved by BS, but not active
Active: the required resources committed by the BS
IEEE 802.16 MAC “ CPS “ Uplink Service Classes
UGS: Unsolicited Grant Services
rtPS: Real-time Polling Services
nrtPS: Non-real-time Polling Services
BE: Best Effort
IEEE 802.16 MAC “ CPS “ Uplink Services: UGS
UGS: Unsolicited Grant Services
For CBR or CBR-like services, e.g., T1/E1.
The BS scheduler offers fixed size UL BW grants on a real-time periodic basis.
The SS does not need to send any explicit UL BW req.
IEEE 802.16 MAC “ CPS “ Uplink Services: rtPS
rtPS: Real-time Polling Services
For rt-VBR-like services, e.g., MPEG video.
The BS scheduler offers real-time, periodic, UL BW request opportunities.
The SS uses the offered UL BW req. opportunity to specify the desired UL BW grant.
The SS cannot use contention-based BW req.
IEEE 802.16 MAC “ CPS “ Uplink Services: nrtPS
nrtPS: non-real-time polling services
For nrt-VBR-like services, such as, bandwidth-intensive file transfer.
The BS scheduler shall provide timely (on a order of a second or less) UL BW request opportunities.
The SS can use contention-based BW req. opportunities to send BW req.
IEEE 802.16 MAC “ CPS “ Uplink Services: BE
BE: Best Effort
For best-effort traffic, e.g., HTTP, SMTP.
The SS uses the contention-based BW request opportunities.
IEEE 802.16 MAC “ CPS “ Bandwidth Grant
IEEE 802.16 MAC “ CPS “ BW Request/Grant Mechanisms
Implicit requests (UGS): No actual requests
BW request messages, i.e., BW req. header
Sends in either a contention-based BW req. slot or a regular UL allocation for the SS;he special B
Requests up to 32 KB with a single message Request
Incremental or aggregate, as indicated by MAC header“
Piggybacked request (for non-UGS services only)
Presented in Grant Management (GM) sub-header in a data MAC PDU of the same UL connection
is always incremental
Up to 32 KB per request for the CID
Poll-Me bit
Presented in the GM sub-header on a UGS connection
request a bandwidth req. opportunity for non-UGS services
IEEE 802.16 MAC “ CPS -- Contention UL Access
IEEE 802.16 MAC “ CPS UL Sub-Frame Structure
IEEE 802.16 MAC “ CPS “ Ranging
Ranging is a process of acquiring the correct timing offset, and PHY parameters, such as, Tx power level, frequency
offset, etc. so that the SS can communicate with the BS correctly.
BS performs measurements and feedback.
SS performs necessary adjustments.
Two types of Ranging:
Initial ranging: for a new SS to join the system
Periodic ranging (also called maintenance ranging): dynamically maintain a good RF link.
IEEE 802.16 MAC “ CPS “ Automatic Repeat reQuest (ARQ)
A Layer-2 sliding-window based flow control mechanism.
Per connection basis.
Only effective to non-real-time applications.
Uses a 11-bit sequence number field.
Uses CRC-32 checksum of MAC PDU to check data errors.
Maintain the same fragmentation structure for Retransmission.
Optional.
IEEE 802.16 MAC “ Privacy Sub-layer (PS)
Two Major Functions:
Secures over-the-air transmissions
Protects from theft of service
Two component protocols:
Data encryption protocol
A client/server model based Key management protocol (Privacy Key Management, or PKM)
IEEE 802.16 MAC “ PS -- Security Associations
A set of privacy information, e.g., encryption keys, used encryption algorithm
Three types of Security Associations (SAs)
Primary SA: established during initial registration
Static SA: provisioned within the BS
Dynamic SA: dynamically created on the fly
Identified by a 16-bit SAID
Connections are mapped to SAs
IEEE 802.16 MAC “ PS -- Multi-level Keys and Their Usage
Public Key
Contained in X.509 digital certificate
Issued by SS manufacturers
Used to encrypt AK
Authorization Key (AK)
Provided by BS to SS at authorization
Used to derive KEK
Key Encryption Key (KEK)
Derived from AK
Used to encrypt TEK
Traffic Encryption Key (TEK)
Provided by BS to SS at key exchange
Used to encrypt traffic data payload
IEEE 802.16 MAC “ PS -- Data Encryption
Use DES (Data Encryption Standard) in CBC (Cipher Block Chaining) mode with IV (Initialization Vector).
CBC IV is calculated from
IV parameter in TEK keying info; and
PHY synchronization field in DL-MAP.
Only MAC PDU payload (including sub-headers) is encrypted.
MAC PDU headers are unencrypted.
Management messages are unencrypted.
IEEE 802.16 MAC “ one big item is out of scope
Scheduler
Questions ??
References
IEEE802.16-2004
Alcatel White Paper: WiMAX, making ubiquitous high-speed data services a reality
Intel White Paper: Understanding WiMAX and 3G for Portable/Mobile Broadband Wireless
WiMAX Forum: wimaxforum.com
http://en.wikipediawiki/WiMax
IEEE 802.16 MAC “ commonly used terms
BS “ Base Station
SS “ Subscriber Station, (i.e., CPE)
DL “ Downlink, i.e. from BS to SS
UL “ Uplink, i.e. from SS to BS
FDD “ Frequency Division Duplex
TDD “ Time Division Duplex
TDMA “ Time Division Multiple Access
TDM “ Time Division Multiplexing
OFDM “ Orthogonal Frequency Division Multiplexing
OFDMA - Orthogonal Frequency Division Multiple Access
QoS “ Quality of Service
read more
http://en.wikipediawiki/Wireless_broadband
http://bwianews
http://wi-fiplanetwimax/article.php/3412391/WiMAX-Broadband-Wireless-Access.htm
Why WiMAX?
WiMAX covers a couple of different frequency ranges. Basically, the IEEE 802.16 standard addresses frequencies from 10GHz to 66GHz. The 802.16a specification, which is an extension of IEEE802.16, covers bands in the 2GHz-to-11GHz range. WiMAX has a range of up to 30 miles with a typical cell radius of 4“6 miles.
WiMAX's channel sizes range from 1.5 to 20MHz as well, and offer a WiMAX-based network the flexibility to support a variety of data transmitting rates such as T1 (1.5Mbps) and higher data transmitting rates of up to 70Mbps on a single channel that can support thousands of users. This flexibility allows WiMAX to adapt to the available spectrum and channel widths in different countries or licensed to different service providers.
WiMAX supports ATM, IPv4, IPv6, Ethernet, and VLAN services. So, it can provide a rich choice of service possibilities to voice and data network service providers. In addition, WiMAX provides an ideal wireless backhaul technology to connect 802.11 wireless LANs and commercial hotspots with the Internet.
The WiMAX-based solution is set up and deployed like cellular systems using base stations that service a radius of several miles/kilometers. The most typical WiMAX-based architecture includes a base station mounted on a building and is responsible for communicating on a point to multi-point basis with subscriber stations located in business offices and homes. The customer premise equipment (CPE) will connect the base station to a customer as well; the signal of voice and data is then routed through standard Ethernet cable either directly to a single computer, or to an 802.11 hot spot or a wired Ethernet LAN.
WiMAX-based solutions include many other advantages, such as robust security features, good QoS (Quality of Service), and mesh and smart antenna technology that will allow better utilization of the spectrum resources. Also, the WiMAX-based voice service can work on either traditional Time Division Multiplexed (TDM) voice or IP-based Voice, also known as Voice over IP (VoIP).
WiMAX Connectivity and Solutions
WiMAX allows equipment vendors to create many different types of IEEE802.16-based products, including various configurations of base stations and customer premise equipment (CPE). WiMAX also allows the services provider to deliver many types of wireless access services. The WiMAX can be used on a variety of wireless broadband connections and solutions:
"Last Mile" Broadband Access Solutionâ€Metropolitan-Area Networks (MAN) connections to home and business office, especially in those areas that were not served by cable or DSL or in areas where the local telephone company may need a long time to deploy broadband service. The WiMAX-based wireless solution makes it possible for the service provider to scale-up or scale-down service levels in short times with the client request.
Backhaul networks for cellular base stations, bypassing the Public Switched Telephone Network (PSTN); the cellular service providers can look to wireless backhaul as a more cost-effective alternative. The robust WiMAX technology makes it a nice choice for backhaul for enterprises such as hotspots as well as point-to-point backhaul solutions.
Backhaul enterprise connections to the Internet for WiFi hotspots. It will allow users to connect to a wireless Internet service provider even when they roam outside their home or business office.
A variety of new business services by wireless Internet service provider.
