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BER Performance of CDMA, WCDMA, IEEE802.11g in AWGN and Fading Channels M.A.ARCHANA, Dr.C.PARTHASARATHY, C.V.S RAVI TEJA maarchaname@gmail.com, drsarathy45@gmail.com , ravi.teja2394@gmail.com ABSTRACT
standards, including slot synchronization, frame synchronization with code group identification and scrambling code identification. In CDMA 2000, a pilot channel is spread by a PN code with cellspecific code phase to help timing synchronization between mobile and base stations. In 802.11g, a Barker code is applied to detect bit boundary before packet identification. In this paper we have illustrated through simulation results of the level of power consumption of different wireless communication standards applicable in AWGN and fading channels. 1.1Additive White Gaussian Noise (AWGN) Channel: accounts only for white noise and does not accounts for fading frequency selectivity, interference and dispersion. BSC channel corrupt a binary signal by reversing each bit by a fixed probability p. Multipath fading channel include multipath scattering effects, time dispersion, and Doppler shifts that arise from relative motion between the transmitter and receiver. CDMA-2000 is a terrestrial radio interface of 3G wireless communication and specifications developed by 3GPP2. It is basically developed within the specification of IMT-2000 of international telecommunication union (ITU) and is backward compatible and well suited for global roaming. CDMA-2000 physical layer includes several modes of operations as per the requirement of user and local conditions. 1.2 Fading Channel: The rapid fluctuation of the amplitude of a signal over a relatively small distance is referred to as fading. Interference between two or more versions of the transmitted signal can result in different propagation delays at the receiver and this is known as multipath. Fading channel models are often used to model the effects of electromagnetic transmission of information over the air in cellular networks and broadcast communication. Fading channel models are also used in underwater acoustic communications to model the distortion caused by the water.
In recent years wireless communication plays a vital role in the world, it makes us relax from the overhead of cables. Nowadays WCDMA, CDMA2000, and IEEE 802.11g systems receive a great deal of attention in wireless communications. One of the common parts of these three systems is the direct-sequence code-division multiple access (DS-CDMA) technology. In DS-CDMA systems, pseudo noise (PN) code synchronization is one of main challenges due to its code length. PN codes are usually used to identify channels during communications. Before a handset starts to receive system broadcast channels, a code synchronization process is necessary to achieve codes, timing, and frequency synchronization with the target cell site and vice versa, also the tremendous increase in usage of wireless communication. In this paper we propose an integrated code synchronizer for WCDMA, CDMA 2000, IEEE 802.11g which is designed by applying three low power techniques such as power management, absolute weighted magnitude calculation and spurious power suppression adder. In addition, a common combined scheme is used to evaluate the bit-error-rate performance of the different wireless Standards, both in AWGN and fading channels. Simulation results are being obtained using MATLAB. Key words: WCDMA, CDMA 2000, IEEE 802.11g, Absolute Weighted Magnitude Calculation, Spurious Power Suppression Adder, AWGN, Fading channel. 1 INTRODUCTION WCDMA, CDMA2000 and 802.11 g system receive a great deal of attention in wireless communications. This paper is divided into three parts such as code synchronizations for three different systems. In WCDMA, a three-stage code synchronization process is implemented in 3 GPP
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number of channels. Each channel has an equal bandwidth and is determined by the target data bit rate and the modulation scheme used. A transmitter sends data from each channel for a fixed amount of time called the dwell time. There are two types of frequency hopping slow frequency hopping and fast frequency hopping. The main advantage of frequency hopping over DSSS is its flexibility to use and alternative channel within the allocation band .Typically there are 22 hop patterns and 79 no overlapping frequency channels with 1 MHz channel spacing. 2.3.3 Direct Sequence Spread Spectrum (DSSS) Direct Sequence Spread Spectrum (DSS) is modulation techniques in which a message signal is spread over a bandwidth that is typically much greater than that required for reliable communications. . DSSS PHY is the part of PHY layer works on 2.4 GHz frequency band. Data transmission is run through the DSSS PMD sub layer. The DSSS PMD get binary bits information from the PLCP protocol data unit (PPDU) then change into RF signals for the wireless medium by the help of carrier modulation and DSSS techniques. The PLCP preamble and PLCP header send 1 Mbps with differential binary phase shift keying (DBPSK) and MPUD send at either 1Mbps or 2Mpbs both uses differential quadrature phase shift keying (DQPSK) modulation techniques. DSSS techniques also use in cellular network (CDMA), Global Positioning System (GPS). 2.3.4 Orthogonal Frequency Division Multiplexing (OFDM) OFDM is a multi-carrier modulation technique which is used to transmitted single data stream over a number of lower rate subcarrier either modulation or a multiplexing technique. IEEE 802.11’s standard adopted OFDM technology because of transmission high-rate wireless local area networks (WLANs).The main reasons to merged OFDM in IEEE 802.11 is to increase the robustness against frequency selective fading and narrow interference. There are some more features concerned with the OFDM technology are: High spectral efficiency Great flexibility Confirmation to available channel bandwidth
2 TECHNOLOGIES USED WCDMA, CDMA2000, and IEEE 802.11g are the three different types of wireless standard technologies used. 2.1 WCDMA W-CDMA (Wideband Code Division Multiple Access) is a wideband spread-spectrum channel access method that utilizes the directsequence spread spectrum method of asynchronous code division multiple accesses to achieve higher speeds and support more users compared to most time division multiple access (TDMA) schemes used today. 2.2 CDMA2000 CDMA2000 is a family of 3G mobile technology standards, based on CDMA, to send voice, data, and signaling data between mobile phones and cell sites. CDMA2000 is also known as IMT Multi -Carrier (IMT-MC)) 2.3 IEEE 802.11g The IEEE 802.11g wireless standard protocol is growing rapidly worldwide and become the most mature technology for WLANs. The IEEE 802.11g standard consists of detailed specifications for both the medium access control (MAC) and three physical layers (PHY). The PHY layer selects the correct modulation scheme that provides spread spectrum in channel accessibility, data rate as well as the necessary bandwidth. The IEEE 802.11g physical layer uses basically four types of wireless data exchange techniques: Infrared (IR) Frequency hopping spread spectrum (FHSS) Direct sequence spread spectrum (DSSS). Orthogonal Frequency Division Multiplexing (OFDM) 2.3.1 Infrared (IR) IR transmission operate at wavelength near 850nm.The IR signal is produced either by semiconductor laser diodes or LEDs with the former being preferable because their electrical to optical conversion behavior is more liner. The infrared technology is not successfully commercialized. 2.3.2 Frequency hopping spread spectrum (FHSS) Frequency hopping spread spectrum (FHSS) is to divide the allocated frequency band into a
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2.3.5 Bit error rate Bit error rate is a method of assessing the digital wireless transmission and thus is a very good way of increasing the system integrity and even the robustness can be improved by calculating the bit error rate and if it is below a certain threshold, steps can be taken to improve it
3.2 CDMA 2000 In CDMA2000, Pilot channel is spread by a PN code with length of 32 768 chips. It is not necessary to detect all 32 768 chips. There is a tradeoff between hardware Complexity and correct detection rate. We decide to detect 128 chips of the PN code in a CDMA2000 system to achieve the hardware efficiency as well as the detection rate. Figure 3. 2 shows the generalized model
Bit Error rate = Number of errors / Number of bits transmitted
3 PROPOSED SYSTEM 3.1 WCDMA In WCDMA, the code synchronization is divided into a three stage process Primary synchronization code, secondary synchronization codes have to be identified by active correlator. Scrambling code is identified by ballot machine. Stage 1 has to detect a 256-chip primary synchronization code (PSC). Generally, the matched filter is used to detect the slot boundary, and the correlation results are further accumulated for 15 slots to improve the signal-to-noise ratio (SNR). Stage 2, one of 16 secondary synchronization codes (SSCs) has to be identified by active correlator for further comma-free Reed–Solomon decoding. Stage 3, one of eight complex-valued scrambling codes is identified as the cell-specific scrambling code by ballot machine. Figure 3. 1 shows the generalized model for the three stages. First, input data are correlated with local generated PN code sequence. Then, correlation results are calculated and accumulated, and the maximal result is identified as the desired timing or the local PN code is identified as the desired one by the peak detector.
Figure 3.2 CDMA2000 Code Synchronizer Model 3.3. IEEE 802.11g In 802.11 g, bit boundary is identified through Barker code detection. Accordingly, an 11chip detection of Barker codes is applied to 802.11 g code synchronization. A synchronization fieldmatched filter is employed to calculate the correlations between and Barker codes. When the peak detector generates periodic peak values, Barker codes are located. Figure 3. 3 shows the generalized model.
Figure 3.3 IEEE 802.11 g Code Synchronizer Model
4. DESIGN METHODOLOGY 4.1 System Architecture According to the models of Figures 3. 1–3.3, the integrated synchronizer for WCDMA, CDMA2000, and 802.11 g is generalized, and the overall model is shown in Figure 4.1. Input data are correlated. With local generated PN-code sequences. Then, correlation results are calculated and accumulated, and the peak result is identified as the desired timing or the local PN code is identified as the desired one. Note that only necessary hardware blocks in this generalized model are enabled when operating in different systems
.
Figure 3.1 WCDMA Code Synchronizer Model
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calculating the CE’s .So applying low power techniques in the design of the adders to improve the power dissipation of the synchronizer Techniques: 1.A spurious power suppression technique (SPST) 2. Absolute weighted magnitude 3.Power management. Figure 4.2 illustrates a spurious power suppression technique (SPST) adder in which it is further divided into most significant part (MSP) and least significant part (LSP) sub adders to reduce adder operations. This SPST adder is especially effective for PN-code synchronizations since it mostly results in very small values. 5 RESULTS For performing simulations, simulation was developed under MATLAB 7.0 environment. This work is mainly dependent on the bit error rate performance of the system when the signal is passed through the AWGN and fading channels under the three different wireless communications technologies viz. WCDMA, CDMA2000 and IEEE 802.11g. Figure 5.1 illustrates the Power consumption in the CE array of WCDMA technology in AWGN channel with and without low power technique. Spurious power suppression technique has reduced half of the power in the AWGN channel. Figure 5.2 illustrates the power consumption Power consumption in the CE array of WCDMA technology in Fading channel with and without low power technique. When compared to AWGN channel fading channel has consumed less power.
Figure4.1 System Architecture 4.2 Spurious Power Suppression Technique The adders in the RCU design, uses spurious power suppression technique, are separated into two parts namely the most significant part (MSP) and the least significant part (LSP) between the eighth and the ninth bits. The adder is designed such that it latches the input data of the MSP whenever it doesn’t affect the computation results. By eliminating the computation in MSP, it not only save power consumption inside the adder in the current stage but also reduce the glitching noises which occurs in the arithmetic units in the next stage. The detection logic unit and SE unit is used to determine the effective input ranges of the operands and used to compensate the sign signals respectively.
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Figure 4 .2 Low power adder design using spurious power suppression technique 4.3 Correlation Element Array It is composed of 16 rows, each row include 16 CE’s So CE Array contains 256 CE’s It is configured to work in 2 modes Active mode: partial results are fed back to its input to execute self accumulated correlations. Passive mode: Serially linked CE’s form a matched filter. 256 CE’s are linked into chain 4.4 Code synchronization Most of the power consumption occurs only in CE array. Adders play an important role when
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Figure 5.1 Power consumption in the CE array of WCDMA technology in AWGN channel 40 35
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Figure 5.2 Power consumption in the CE array of WCDMA technology in fading channel
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Figure 5.3 illustrates the power consumption in the CE array of CDMA2000 technology in AWGN channel with and without spurious power suppression technique. Figure 5.4 illustrates the power consumption in the CE array of CDMA2000 technology in fading channel. When compared to AWGN channel fading channel has consumed less power and the proposed design has low effect on the control of power consumption by the system.
Figure5.5 Power consumption in the CE array IEEE 802.11g of technology in fading channel 40
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Figure 5.6 Power consumption in the CE array of IEEE 802.11g technology in fading channel
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Thus at last we are going to show the bit error rate performance of the system when the signal is passed through the AWGN and fading channels in figure 5.7 and figure 5.8 respectively.
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Figure 5.3 Power consumption in the CE array of CDMA2000 technology in AWGN channel
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Figure 5.7 BER of WCDMA, CDMA2000, 802.11g in AWGN and fading channels without spst
Figure 5.4 Power consumption in the CE array of CDMA2000 technology in fading channel Figure 5.5 illustrates the power consumption in the CE array of IEEE 802.11g technology in AWGN channel with and without spurious power suppression technique. Figure 5.6 illustrates the power consumption in the CE array of IEEE 802.11g technology in fading channel. The power consumed in this technology is very much lower, When compared to WCDMA, CDMA2000.
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6 CONCLUSIONS
In this paper, the proposed Scheme of adding Spurious power suppression technique to the
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code synchronizer shows the results that the power consumption can be reduced to 56.27% in WCDMA, 5.86% in CDMA2000 synchronization, and 83.98% in 802.11 g synchronization, respectively. Moreover, the proposed Scheme takes the system integration issues into account by balancing the data I/O rate and the data processing rate through an interlaced I/O schedule. REFERENCES
[10] K. H. Chen, Y. M. Chen, and Y. S. Chu, “A versatile multimedia functional unit design using the spurious power suppression technique,” in Proc. IEEE Asian Solid-State Circuits Conf., 2006, pp. 111–114. [11] Nisha D, Divya K, Saranya K “A Low Complexity Image Scaling Processor Using Spurious-Power Suppression Technique,”in proc International Journal of Advanced Research in Computer and Communication Engineering Vol. 3, Issue 3, March 2014, pp 5228-5232. [12] Jaspreet kaur, Manish Jaiswal, Anuj Kumar Sharma, Vikash Singh, Udit Gupta,” Performance Analysis of IEEE WLAN 802.11a in Presence of Different FEC”, in proc Conference on Advances in Communication and Control Systems 2013 , pp 642646.
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