_Code_Division_Multiple_Access_CDMA_System_in_Multipath_Environment.doc - Code Division Multiple Access(CDMA System in Multipath Environment Vidya kant


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Code Division Multiple Access (CDMA) System in Multipath Environment Vidya kant Dwivedi 1 Manoj KR Shukla 2 1 Senior Lecturer , United College of Engg. & Research, Allahabad 2 Research Scholar, Deptt. of ECE, MNNIT, Allahabad Key words: CDMA, Spread spectrum, Bit Error Rate, Multipath fading ABSTRACT Many Digital cellular and mobile systems are in use today. Analog cellular systems use Frequency Division Multiple Access (FDMA) technique. Digital systems use Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA) and Code Division Multiple Access (CDMA) techniques [1]. CDMA system separates users through the assignment of different code sequences. These sequences should have low cross correlation properties and should allow the multipath effects commonly found in wireless channels. CDMA system uses the idea of tolerating interference by Spread spectrum modulation (spreading the spectrum) [1, 6]. In this paper simulation of CDMA system has been described which is operating in multipath environment by considering thermal noise and interference. The simulation results are analyzed using Ricean K factor (Racian K factor is a factor that measures propagation loss in multipath fading environment). 1. Introduction Multiple access schemes [1, 6] allow multiple users to access the services. One type of multiple access system is, in which a large number of users share a common communication channel to transmit information to a receiver. This can be done by different methods, viz., Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), and Code Division Multiple Access (CDMA) [1, 6]. Frequency Division Multiple Access (FDMA), First Generation (1G) cellular communication networks [2, 7] is an analogue transmission technique used for mobile phone communications, in which the frequency band allocated to a network is divided into sub-bands or channels. Each frequency channel can carry either a voice conversation or digital data, and one channel will be assigned to each subscriber for the duration of a call. Using FDMA in this way, multiple users can share the available band without the risk of interference between the simultaneous calls. Time Division Multiple Access (TDMA) is digital transmission technology that allows a number of users to access a single radio frequency (RF) channel without interference by allocating unique time slots to each user within each channel. The TDMA digital transmission scheme multiplexes three signals over a single channel. The current TDMA standard for cellular divides a single channel into six time slots, with each signal using two slots, providing a 3 to 1 gain in capacity over advanced mobile-phone service (AMPS). 1
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Each caller is assigned a specific time slot for transmission. This technique is used in second generation (2G) cellular communication networks [2, 7].
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  • Spring '17
  • Dr.Alif

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