AUTO3120
Enhancing WIMAX
System Design Performance with
FPGAs
Seminar Presentation
Samuel Ailen-Ubhi T94766
University of Vaasa
04.10.2011
WIMAX
Worldwide
Interoperability for
Microwave Access
Contents of WiMAX Seminar
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WiMAX Overview
WiMAX Infrastructure
WiMAX and Standards
WiMAX Forum
WiMAX Protocol architecture
Physical layer
Medium Access layer
WiMAX System Design with FPGAs
What is WiMAX?
- Protocol of communication network without wire.
- Allows communications over long distances with greater
bandwidth than WiFi, and also a method for providing backhaul to
WiFi.
WiMAX
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Provides high-speed Internet access to home and business subscribers,
without wires.
Frequency range of10-66 GHz LoS and additional range of 2- 11 GHz
NLoS.
It Supports Legacy voice systems, voice over IP, TCP/IP, applications with
different QoS requirements etc.
It consists of access point, BS(Base Station) and SSs (Subscriber Stations).
All data traffic goes through the BS, and the BS control the allocation of
bandwidth on the radio channel.
During a communication, all the information coming from an SS go to the
BS and are retransmitted back to the right SS.
Base stations (BS) can handle thousands of subscriber stations (SS).
Two type of link are defined:
– The downlink: From the BS to the SS.
– The uplink: From the SS to the BS.
WiMAX Infrastructure
• A WIMAX tower: similar in concept to a cell-phone tower. A single
WIMAX tower can provide coverage to a very large area (50 km).
• A WIMAX receiver : The receiver and antenna could be a small box or
PCMCIA card, or could be built into a laptop.
WiMAX and Standards
• 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
WiMAX and Standards
IEEE 802.16e-2005 improvements upon IEEE 802.16-2004
• Adding support for soft and hard handover between base stations
(mobility)
• Advanced antenna diversity schemes, and hybrid automatic repeatrequest (HARQ)
• Adaptive Antenna Systems (AAS) and MIMO technology
• Introducing downlink sub-channelization,
• allowing administrators to trade coverage for capacity or vice versa
• Adding an extra QoS class for VoIP applications
• IEEE 802.16e-2007: Management Plane Procedures and Services- in
progress
• IEEE 802.16e-2009: Air Interface for Fixed and Mobile Broadband
Wireless Access System- in progress
WiMAX Forum
• Not-for-profit organization
• Formed to certify and promote the compatibility and interoperability of
broadband wireless products based upon the harmonized IEEE
802.16/ETSI Hiper MAN standard.
• WiMAX Forum Certified™ products are fully interoperable and support
broadband fixed, portable and mobile services.
• The WiMAX Forum has hundreds of members, comprising the majority
of operators, component vendors and equipment vendors in the
communications ecosystem• AT&T, British Telecom, Fujitsu, Intel,
Motorola, Nokia, Samsung, Lenovo, Sharp Corporation, LG Electronics etc
• “WiMAX Forum” is aregistered trademark.
WiMAX Protocol architecture
• Physical Layer
• Medium Access Layer
Physical layer
Physical layer
• The flow of bits is structured as a sequence of frames of equal length.
• There is a downlink subframe and an uplink subframe and two modes of
operation.
• 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
Physical layer
• Orthogonal Frequency Division Multiplexing Access(OFDM/OFDMA)
where the spectrum is divided into many sub-carriers
• Each sub-carrier then uses QPSK or QAM for modulation Scalable
OFDMA (SOFDMA) to support scalable subcarrier bandwidths from 1.25
to 20 MHz
• Sub-carrier spacing at 10.94 kHz.
• OFDMA spreads the energy of an impulse noise over a WiMAX-OFDMA
burst. This means that instead of a few symbols being lost, the noise
level slightly increases over a burst, which may not cause an increase in
the error-rate.
WiMAX Protocol architecture
• The MAC is comprised of three sublayers.
• The Service Specific Convergence Sublayer (CS) provides any
transformation or mapping of external network data, received through
the CS service access point (SAP), into MAC SDUs received by the MAC
Common Part Sublayer (MAC CPS) through the MAC SAP.
• The Common Part exchanges MAC service data units (SDUs) with the
Convergence layer.
• The Security sub layer addresses authentication, establishment of keys
and encryption and exchanges MAC PDUs with the Physical layer.
Physical and MAC layers
Physical and MAC layers
• Overview of PHY Layer functions in a typical WiMAX base station
Physical layer Security Threat
• Jamming attack: achieved by introducing a source of noise strong enough
to significantly reduce the capacity of the channel
• Solution: prevent jamming attack by increasing the power of signals or
by increasing the bandwidth of signals using spreading techniques such
as frequency spread spectrum
• Scrambling attack: scrambling is a kind of jamming but only provoked for
short intervals of time and targeted to specific WiMAX frames or parts of
frames at the PHY layer.
• Solution: we can use anomalies monitoring beyond performance norm
(or criteria) to detect scrambling
• Water torture attack: this is also a typical attack in which an attacker
force a SS to drain its battery or consume computing resources by
sending a series of bogus frames.
• Solution: a sophisticated mechanism is necessary to discard bogus
frames, thus avoiding running out of battery or computational resources.
MAC Security Threat
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Eavesdropping of management messages.
BS or MS masquerading.
Management message modification.
Man in the middle attack.
Denial of Service attack.
Solutions: Key authentication. Countermeasures need to be devised for
networks using the security options with critical or major risks. An
intrusion detection system approach can be used to address some of the
threats. More research is needed in this direction.
WiMAX System Design with FPGAs
• Hardware Platform for WiMAX Implementation- Challenges
- Processing speed: Hardware platform must have significant
processing capabilities to support high data rate.
- Flexibility: WiMAX is a relatively a new market and still
undergoing it product life cycle in the
development/deployment stage.
- Time to Market: This has a direct effect on the
development life cycle and choice of hardware platform.
- Cost Reduction Path: Plans to use resources and to access
the final stage after the initial uncertainty surrounding it
should also be considered.
Field programmable gate arrays -Stratix II
Device Floorplan
• Altera’s Stratix II FPGA, are usually used at the heart of high-bandwidth
systems to accelerate performance and enable new functionality
• Stratix II devices improve on the features that set new standards in
FPGAs
Field programmable gate arrays Stratix II Device Floorplan
• Up to 9 Mbits of memory in three block sizes: M-RAM, M4K,
and M512 blocks
• Includes parity bits for error checking
• Performance up to 370 MHz
• Mixed-width data and mixed-clock modes
• Maximized performance of up to 370 MHz providing DSP
throughput up to 284 GMACs
• Up to 12 PLLs (four enhanced PLLs and eight fast PLLs) per
device to provide spread sspectrum, programmable
bandwidth, clock switchover, real-time PLL reconfiguration,
and advanced multiplication and phase shifting
• Remote system upgrades for reliable and safe deployment of
in-system upgrades and bug fixes
WiMAX System Design-FPGA
• Overcoming WiMAX system design implementation
challenges with FPGAs.
• Processing Speed:
- High performance FPGAs contain embedded DSP blocks,
TriMatrix memory architecture, innovative logic structure,
and high-speed interfaces.
- These features provide powerful and integrated platform
to implement broadband wireless systems such as WiMAX.
- Each DSP block can support a variety of multiplier bit sizes
and operation modes .
Stratix II DSP Block Architecture
WiMAX System Design-FPGA
• Flexibility:
- Altera’s Stratix II FPGAs provide the ability to easily evolve
WiMAX systems in accordance with changing market
demands.
- These devices allow remote system upgrades to be
transmitted over any communications network.
- Remote system upgrades are enabled using Stratix II devices
and flash memory
WiMAX System Design-FPGA
• Time-to-Market
- key differentiator for developing WiMAX compliant
products.
- To achieve this, designers need access to off-the-shelf IPs
and reference designs that help accelerate their own
development cycle
- some of the PHY layer solutions available from Altera :
a. Forward Error Correction (FEC)
b. OFDM modulation/demodulation
c. Multiple Antenna Techniques
WiMAX System Design-FPGA
• Cost Reduction Path
- Altera provides this cost reduction path for its FPGAs
through HardCopy devices.
- Altera HardCopy devices are the industry’s first structured
ASICs that offer a comprehensive alternative to traditional
ASICs
- Altera provides FPGAs, development tools, intellectual
property (IP), and a seamless migration path from the
function-verified prototypes to high-volume production
devices.
Conclusions
• WiMAX is an emerging technology with significant potential
broadband wireless internet access market
• The diverse hardware requirements including processing
speed, flexibility, integration and time-to market necessitate
an FPGA based implementation platform.
Summary
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WiMAX Overview
WiMAX Infrastructure
WiMAX and Standards
WiMAX Forum
WiMAX Protocol architecture
Physical layer
Medium Access layer
WiMAX System Design with FPGAs
Thank You
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: www.wimaxforum.com
• http://en.wikipedia.org/wiki/WiMax
• Stratix II Device Family Features:
http://www.altera.com/products/devices/stratix2/features/st2features.html
• www.altera.com/literature/wp/wp_wimax.pdf
• www.altera.com/literature/hb/stx2/stx2_sii51001.pdf