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?

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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

• • • • • • • •

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.

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The uplink: From the SS to the BS.

WiMAX Infrastructure

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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)

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Air Interface for Fixed Broadband Wireless Access System MAC and PHY Specifications for 10 – 66 GHZ (LoS)

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One PHY: Single Carrier

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Connection-oriented, TDM/TDMA MAC, QoS, Privacy IEEE 802.16a (January 2003)

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Amendment to 802.16, MAC Modifications and Additional PHY Specifications for 2 – 11 GHz (NLoS)

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Three PHYs: OFDM, OFDMA, Single Carrier

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Additional MAC functions: OFDM and OFDMA PHY support, Mesh topology support, ARQ IEEE 802.16d (July 2004)

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Combines both IEEE 802.16 and 802.16a

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Some modifications to the MAC and PHY IEEE 802.16e (2005)

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Amendment to 802.16-2004

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MAC Modifications for limited mobility

WiMAX and Standards

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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 repeat request (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

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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

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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)

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Downlink & Uplink time share the same RF channel

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Dynamic asymmetry

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does not transmit & receive simultaneously (low cost) Frequency-Division Duplex (FDD)

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Downlink & Uplink on separate RF channels

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Full Duplexing (FDX): can Tx and Rx simultaneously;

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Half-duplexing (HDX) SSs supported (low cost

Physical layer

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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

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Overview of PHY Layer functions in a typical WiMAX base station

Physical layer Security Threat

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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

• • • • • •

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

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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

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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

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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

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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

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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

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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

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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/st2 features.html

www.altera.com/literature/wp/wp_wimax.pdf

www.altera.com/literature/hb/stx2/stx2_sii51001.pdf