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The Enhanced Data Rates for Global Evolution system known in short as EDGE is considered as a major step towards reaching 1 1 1 3G mobile communications services. The EDGE system, usually referred to as the 2% G, promises users with data rates reaching 3S4 Kbps versus only 9.6 Kbps in the well-known GSM system. In order to achieve such high data rates, two methods are used in the EDGE system to increase the throughput obtained by each user of the system, these are Link Adaptation (LA) and Incremental Redundancy (IR).In this paper, we explain how these methods are applied in the EDGE system and we introduce a new proposal for modifying the existing EDGE coding schemes based on the use of convolutional codes to schemes based on the use of Turbo codes to firther increase the throughput and consequently increase the data rates obtained. I. INTRODUC~IONMobile communi&tions has grown explosively in the last decade. This is demonstrated by the fact that at the end of the year 2000, the number of mobile subscriirs has exceeded ,700 million worldwide and this number is even expected to grow further reaching about 1600 million by the year 2005 [I]. So far, m d Y speech senices. have been provided to the subscribers, However, everyday, subscribers get more eager to receive new XMces, which are currently unavailable. Namely, there is a demand for a shift from ''voice-centric s e w i d to niultimedia-oriented (voice, data, video, fax) services." [2]. These new senices can not be achieved except at highdata rates, hence research was conducted in order to find ways to maximize the throughpld delivered to each user of the system. Throughput is simply defined as the ratio between the amount of useful information and the total amount of information transmitted (nseful information in addition to the redundant information added for the purpose of error detection and correction). The two main methods which are pfO@ to be used in the EDGE system for throughput maximization are Link Adaptation (LA) and Incremental Redundancy (IR) [3-6, 81. The idea of LA is relatively easy; it is based on the fact that the w k k s S communications channel is actually time-vaqing in its nature. Hence, using the same protection scheme all the time will result in a degradation in throughput, but changing the protection scheme in amrdance with the changes in the channel will guarantee that maximum throughput is always obtained 12-51. Upon receiving a packet from the transmitter, the receiver tries to estimate the current channel conditions from the received +d and consequently, the BER is calculated. Thii BER estimate is then passed on to the transmitter via an error-ftee feedback channel. Based on this BER estimate, the " m i t t e r chooses a new coding rate that is o p t i " in the sense that it offers the maximum thronghput that can be obtained among the available d e rates. The o@on

A novel expression for the probability of detection in spectrum-sensing cognitive radio systems is derived over the extended generalised-K composite fading channel assuming energy detection is employed. The new tractable expression subsumes several fading and shadowing environments as special cases. It can also be easily evaluated using commercial software packages such as MATHEMATICA © and MATLAB © .

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