USE_OF_DSP_FOR_WIRELESS_AND_MOBILE.ppt
- 1. USE OF DSP FOR WIRELESS AND MOBILE COMMUNICATION BY RAJAT KUMAR RISHABH SHRIVASTAVA SACHIN KUMAR SINGH SHIV MOHAN GUPTA VINAY SONKER
- 2. 2 What is Signal Processing? • Example of Signals: – Analog: Speech, Music, Photos, Video, radar, sonar, … – Discrete-domain/Digital: • digitized speech, digitized music, digitized images, digitized video, digitized radar and sonar signals,… • stock market data, daily max temperature data, ... Processing Signal in Signal out Operation, Transformation (Analog or Digital) (Analog or Digital)
- 3. 3 What is Digital Signal Processing? • But what about analog signals? Digital Processing Digital Signal in Digital Signal out Operation, Transformation performed on digital signals (using a computer or other special-purpose digital hardware) Analog Signal in Analog-to- Digital (A/D) Conversion Digital Processing Digital-to- Analog (D/A) Conversion
- 4. 4 Signal Processing Examples Why Go Digital??
- 5. Digital Signal Processing And Its Benefits By a signal we mean any variable that carries or contains some kind of information that can be conveyed, displayed or manipulated. Examples of signals of particular interest are: - speech, is encountered in telephony, radio, and everyday life - biomedical signals, (heart signals, brain signals) - Sound and music, as reproduced by the compact disc player - Video and image, - Radar signals, which are used to determine the range and bearing of distant targets
- 6. 6 Why Use DSP For Wireless Communication? • Wireless Systems requires more and more high performance and higher bandwidth 2.5G 3G 2G Bit Rate Performance ~100MIPS 8-13 Kbps ~10,000MIPS 64-384 Kbps ~100,000MIPS 384-3000 Kbps DSP performance might not be enough for future applications 4G ~1000,000MIPS 10 Mbps – 100+ Mbps
- 7. 7 What are the alternatives • High-performance GPPs with DSP enhancements. – Eliminating the need of a DSP and GPP for many products and thus reducing cost – Example: Pentium 4 • Single Instruction Multiple Data (SIMD) instructions allowing identical operations on multiple pieces of data in parallel. • 144 new special instructions providing advanced capabilities for applications such as 3D graphics, video encoding/decoding, and speech recognition. • Several Data Types (floating/integer) • Multi-Core DSPs • Application Specific Integrated Circuits (ASIC) • Field Programmable Gate Array (FPGA)
- 8. ASIC, FPGA • Uses hard-wired logic with varied architectures according to the application • FPGA • It is a network of reconfigurable hardware with reconfigurable interconnect controlled by a switching matrix
- 9. DSP aspects in Wireless communication • Source Coding (Speech coding) • Detection and matched filtering • Diversity and rake receivers • Multi-user detection • Error Correction
- 10. Speech coding for mobile • To reduce the bit-rate required for transmitting telephone quality speech, a new approach to speechcompression is needed. • Current mobile phones compress to about 13,000 b/s (bit per second) and weaim to achieve 4,000 b/s and lower using a method called 'DAP-STC'. • Compression is generallyachieved by spectrally analysing speech segments to derive a model of the human speech process. • DAP-STC is a new and potentially more accurate way of doing this with a modified speech productionmodel. • A variable bit-rate version achieves an average 2,400 b/s and is suitable for packetised speechas may be transmitted over computer networks.
- 11. Source filter model • Fig.
- 12. The Matched Filter Principle • The optimum receiver for any signal – in Additive white Gaussian Noise – over a Linear Time-Invariant Channel • is ‘a matched filter’: Integrate S Locally stored reference copy of transmit signal Channel Noise Transmit Signal
- 13. The Matched Filter Principle Integrate S Locally stored reference copy of transmit signal for “1” Channel Noise Transmit Signal, either S0(t) for “0” or S1(t) for “1” Integrate S Locally stored reference copy of transmit signal for “0” S1(t) S0(t) Select largest
- 14. Fundamentals of Diversity Reception • What is diversity? • Diversity is a technique to combine several copies of the same message received over different channels. • Why diversity? • To improve link performance
- 15. Methods for obtaining multiple replicas • Site Diversity • Frequency Diversity • Time Diversity • Polarization Diversity • Angle Diversity
- 16. Site (or macro) diversity • Receiving antennas are located at different sites. – Example: at the different corners of hexagonal cell. • Advantage: multipath fading, shadowing, path loss and interference all become "independent“
- 17. Frequency diversity, Time diversity, Angle diversity • Frequency diversity: Each message is transmitted at different carrier frequencies . Time diversity: Each message is transmitted more than once. Useful for moving terminals. Angle diversity: • Waves from different angles of arrival are combined optimally, rather than with random phase • Directional antennas receive only a fraction of all scattered energy.
- 18. Low power implementation of DSP in Mobile Communication • The requirement for extended battery life, reduced size and low electromagnetic interference for mobile communication equipment has led to the development of a novel asynchronous DSP device known as CADRE. • Compiler support for the new device is needed to avoid manual assembly-level programming. • Apart from maximising speed and minimising code size, the compiler is required to produce code which exploits the special features of CADRE to minimise energy consumption.
- 19. Source: “Mobile data feels pressure from the need for speed”, Network News, 2 June 1998 (CAP Gemini, September 1999) Mobile Communications Networks First Generation • Analogue • Basic voice telephony • Low capacity • Limited local and regional coverage • E.g. NMT, AMPS, TACS, C-net • Digital: – Circuit switched • Voice plus basic data applications: – Fax – SMS (small message services) – Circuit-switched data • Low data speed • Regional coverage, with trans-national roaming • E.g. GSM, D-AMPS, PDC, IS 95 CDMA • Digital: – Packet and circuit switched • Advanced data — i.e. multimedia applications • Fast data access • Global coverage • E.g. UMTS (WCDMA, TD/CDMA), IMT- 2000 Second Generation Third Generation Wireless data already be introduced in second generation mobile Development of mobile communications
- 20. A FUNCTIONAL BLOCK DIAGRAM OF GSM PHONE
- 21. The baseband processor’s signal chain.
- 22. MIPS requirement for signal processing in GSM
- 23. 23 DSP Targets: Cell Phone -Speech Coders -Speech Recognition - Equalizers - Antenna noise cancellation -Image enhancement techniques DSP Chip RF Codec Voice Codec RF Receiver Microprocessor Chip Cell Peripherals Controlled by Power Management Unit
- 24. 24 DSP Targets: Voice Over IP DSP Chip Voice Codec Memory (Card or Chip) Audio Coders -MP3 -AC3 -AAC Peripherals Micro processor
- 25. Attraction of DSP comes from key advantages such as : * Guaranteed accuracy: (accuracy is only determined by the number of bits used) * Perfect Reproducibility: Identical performance from unit to unit ie. A digital recording can be copied or reproduced several times with no loss in signal quality * No drift in performance with temperature and age * Uses advances in semiconductor technology to achieve: (i) smaller size (ii) lower cost (iii) low power consumption (iv) higher operating speed * Greater flexibility: Reprogrammable , no need to modify the hardware * Superior performance ie. linear phase response can be achieved complex adaptive filtering becomes possible
- 26. CONCLUSION • Designers of 3G base stations will make use of the DSPs in order to achieve the high performance and flexibility needed for tomorrow’s voice and data applications. • Speech coding is an essential application of digital signal processing in modern day telephony and mobile communications, which employ high data compression ratios.