Baseband analog front-end and digital back-end for reconfigurable multi-standard terminals

Multimedia applications are driving wireless network operators to add high-speed data services such as Edge (E-GPRS), WCDMA (UMTS) and WLAN (IEEE 802.11a,b,g) to the existing GSM network. This creates the need for multi-mode cellular handsets that support a wide range of communication standards, each with a different RF frequency, signal bandwidth, modulation scheme etc. This in turn generates several design challenges for the analog and digital building blocks of the physical layer. In addition to the above-mentioned protocols, mobile devices often include Bluetooth, GPS, FM-radio and TV services that can work concurrently with data and voice communication. Multi-mode, multi-band, and multi-standard mobile terminals must satisfy all these different requirements. Sharing and/or switching transceiver building blocks in these handsets is mandatory in order to extend battery life and/or reduce cost. Only adaptive circuits that are able to reconfigure themselves within the handover time can meet the design requirements of a single receiver or transmitter covering all the different standards while ensuring seamless inter-interoperability. This paper presents analog and digital base-band circuits that are able to support GSM (with Edge), WCDMA (UMTS), WLAN and Bluetooth using reconfigurable building blocks. The blocks can trade off power consumption for performance on the fly, depending on the standard to be supported and the required QoS (Quality of Service) leve

Implementation of Turbo Code with Early Iteration Termination in GNU Radio

Wireless communication systems demand energy efficient and performance optimized error correction scheme. Turbo code, an iterative error correction code, shows strong error correction capability. Many wireless communication systems use Turbo code in their standards due to its near ideal performance. The iterative nature of Turbo decoder introduces additional computations, decoding delay, and power consumption. The number of iterations required to obtain the desired output varies with the channel conditions. Early iteration termination at appropriate time reduces the computational complexity without performance degradation. An early iteration termination based on the absolute value of the mean of extrinsic information has been proposed recently. This technique efficiently terminates the iteration at low and high SNR conditions and also minimizes the half iterations. Software Defined Radio (SDR), a communication system technology, is a common platform that supports various standards. GNU Radio is the software part of SDR that allows implementing various features of communication systems. A low complex Turbo decoder in GNU Radio along with Universal Software Radio Peripheral (USRP) helps to implement real time applications with low decoding delay and reduced complexity. In this paper, Turbo CODEC with early iteration termination has been implemented in GNU Radio platform

Parameter Selection At Run-Time To Optimize Energy Efficiency

Energy efficiency is vital for a mobile terminal. In this paper we investigate how to choose the right parameter settings at run-time so that the energy consumption is minimized while satisfying the required level of service. To use a real world example, the energy consumption of a third generation telephone WCDMA downlink receiver with turbo decoding forward error correction is considered. A trade-off is made between the number of fingers of a rake receiver and the number of iterations of the turbo decoder. A simulation environment is constructed to simulate the system. In this paper we present graphs, with which the trade-off can be easily made

Using Channel Output Feedback to Increase Throughput in Hybrid-ARQ

Hybrid-ARQ protocols have become common in many packet transmission systems due to their incorporation in various standards. Hybrid-ARQ combines the normal automatic repeat request (ARQ) method with error correction codes to increase reliability and throughput. In this paper, we look at improving upon this performance using feedback information from the receiver, in particular, using a powerful forward error correction (FEC) code in conjunction with a proposed linear feedback code for the Rayleigh block fading channels. The new hybrid-ARQ scheme is initially developed for full received packet feedback in a point-to-point link. It is then extended to various different multiple-antenna scenarios (MISO/MIMO) with varying amounts of packet feedback information. Simulations illustrate gains in throughput.Comment: 30 page

Relay communications over frequency-selective fading channels

Wireless communications over long distances can be assisted by a third radio acting as a relay. If the relay is placed close to the source, then the source-relay link will be characterized as a fairly benign additive white Gaussian noise (AWGN) channel. However, the long distance link from relay to destination is susceptible to frequency-selective fading. This thesis explores the design and analysis of a particular relay communication system characterized by a low power source, a relay that is close to the source, and a frequency-selective channel from relay to destination. Because the direct link from source to destination is very weak, it is not exploited, but rather communications is via a traditional two-hop process.;Link design is based on the high speed download packet access (HSDPA) standard, which uses a combination of turbo coding, hybrid-ARQ, and multicode CDMA. To provide further diversity, the relay-destination link uses a secondary spreading code, rake reception, and multiple receive antennas. An extensive analysis was conducted to study the influence of a wide variety of link configurations and channel conditions. The study was accelerated through the use of a quasi-analytical approach based on the concept of information-outage, which allows the link to be simulated without requiring a turbo decoder

Software implementation and performance of UMTS turbo code

In the recent years, there has been a proliferation of wireless standards in television, radio and mobile communications. As a result, compatibility issues have emerged in wireless networks. The size, cost and competitiveness set limitations on implementing systems compatible with multiple standards. This has motivated the concept of software defined radio which can support different standards by reloading the software and implementing computationally intensive parts on hardware, e.g., iterative codes. In a typical communication system, all the processing is done in the digital domain. The information is represented as a sequence of bits which is modulated on an analog waveform and transmitted over the communication channel. Due to channel induced impairments, the received signal may not be a true replica of the transmitted signal. Thus, some error control is required which is achieved by the use of channel coding schemes that protect the signal from the effects of channel and help to reduce the bit error rate (BER) and improve reliability of information transmission. Shannon gave the theoretical upper bound on the channel capacity for a given bandwidth, data rate and signal-to-noise ratio in 1940s but practical codes were unable to operate even close to the theoretical bound. Turbo codes were introduced in 1993 where a scheme was described that was able to operate very close to the Shannon limit. Turbo codes are widely used in latest wireless standards e.g. UMTS and LTE. A basic turbo encoder consists of two or more component encoders concatenated in parallel and separated by an interleaver. The turbo decoder uses soft decision to decode the bits and the decoding is done in an iterative fashion to increase reliability of the decision. In this thesis, the turbo code for the UMTS standard is implemented in MATLAB. Four versions of the Maximum Aposteriori Probability (MAP) algorithm are used in the implementation. The simulation results show that the performance of the turbo code improves by increasing the number of iterations. Also, better performance can be achieved by increasing the frame size or the interleaver size and increasing the signal power. Overall, the designing of turbo codes is a trade-off between energy efficiency, bandwidth efficiency, complexity and error performance