Blind intra-cell interference cancellation (IIC) of the W-CDMA signal at the mobile unit is considered. A new blind interference cancellation technique, based on the subspace projection approach, suitable for the down...
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Blind intra-cell interference cancellation (IIC) of the W-CDMA signal at the mobile unit is considered. A new blind interference cancellation technique, based on the subspace projection approach, suitable for the downlink of any CDMA system is proposed. The receiver is blind in the sense that no prior knowledge of users' spreading codes or even their spreading factors are required. The mobile receiver estimates the effective spreading codes of the interfering users regardless of their spreading factors using fast Walsh transform correlators and uses these information to cancel out the intra-cell multi-user interference. The complexity of the proposed technique is low compared to conventional interference cancellation techniques. Simulation results show a capacity increase of up to 150 % of the original (without IIC) system capacity or up to 12 dB signal to Gaussian noise ratio gain at a fixed capacity (the inter-cell interference is modeled as Gaussian noise).
Orthogonal frequency division multiplexing (OFDM) is applied in systems which transmit a high data rate over multipath fading channels in order to avoid the effort of a channel estimation and equalization required in ...
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Orthogonal frequency division multiplexing (OFDM) is applied in systems which transmit a high data rate over multipath fading channels in order to avoid the effort of a channel estimation and equalization required in a single carrier system. If differential modulation is applied no channel equalization is necessary at all. In this paper, the combination of differential modulation and convolutional channel coding is re-interpreted as a concatenated code in which the differential modulation is the inner code and the convolutional code the outer code. Turbo decoding is applied at the receiver resulting in a signal-to-noise ratio (SNR) gain of more than 3.5 dB compared with classical soft decision Viterbi decoding.
Of the feedforward transmitter diversity methods considered for 3rd generation PCS/cellular systems one such method is known as phase sweeping transmitter diversity (PSTD). Since PSTD does not require a modification o...
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Of the feedforward transmitter diversity methods considered for 3rd generation PCS/cellular systems one such method is known as phase sweeping transmitter diversity (PSTD). Since PSTD does not require a modification of the mobile station receiver, an important feature of this method is compatibility with 2nd generation as well as 3rd generation mobile stations. Furthermore, this method of transmitter diversity does not require specification in a standard. This paper provides an introduction to PSTD as it applies to IS-95 and cdma2000; the form of the received PSTD signal at the mobile station; compatibility issues between 2G and 3G; and link performance for AWGN, Rayleigh, and Ricean channel models.
This paper examines the performance of a coded CDMA system with a minimum mean square error decision feedback (MMSE DF) receiver over a Gaussian channel. In the absence of error propagation the MMSE DF perfectly cance...
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This paper examines the performance of a coded CDMA system with a minimum mean square error decision feedback (MMSE DF) receiver over a Gaussian channel. In the absence of error propagation the MMSE DF perfectly cancels interference from k-1 already detected users. If the information bits are decoded at the receiver and re-encoded before being processed by a feedback filter, the number of erroneous decisions passed to other users can be decreased. This improves interference estimation, hence lowering the bit error rate (BER) and increasing the capacity. Convolutional, trellis and turbo trellis codes are employed to reduce error propagation. The performance of various coded systems is compared for the same bandwidth and maximal spectral efficiency.
A new RFID system for the ISM band at 24 GHz employing quasi-optical beam forming is presented. Active integrated antennas are used as transmitters resulting in exceptionally small size of the ID-tags. Identification ...
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A new RFID system for the ISM band at 24 GHz employing quasi-optical beam forming is presented. Active integrated antennas are used as transmitters resulting in exceptionally small size of the ID-tags. Identification codes are transmitted via a spread-spectrum modulated subcarrier that allows for very simple free running microwave oscillators as well as simple but highly selective receiver concepts. A dielectric lens and a 5/spl times/5 rectenna array comprise an imaging receiver that not only identifies but also localizes the tags with an angular resolution better than 3/spl deg/ at a distance up to 14 meters.
The primary objective of developments in wireless communications systems is to increase the density of subscribers simultaneously served by the system. Another major objective is to provide services where high rates o...
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The primary objective of developments in wireless communications systems is to increase the density of subscribers simultaneously served by the system. Another major objective is to provide services where high rates of data transmission are needed. This can be achieved by extending the multiple access scheme and by improving channel modulation and coding. There are two major approaches to the multiple access scheme problem-the code division multiple access (CDMA) and the spatial division multiple access (SDMA). Their implementation calls for the use of smart antennas not only at the base station site, but also at the terminals, where antennas of an improved design are recommended. However, the functioning of smart antennas is still far from being well defined, and in this context a variety of concepts have been examined. This paper presents some results of our investigations into terminal antennas with improved properties of their radiation patterns. We focused on two properties-the optimized shape of the radiation pattern and the scanning of the main beam. These properties are needed to suppress interference. Furthermore, owing to the achieved antenna directivity it is feasible to suppress the scattered waves and to decrease intersymbol interference, which is a prerequisite to achieve a high data transmission rate. Unfortunately, each terminal antenna design must comply with the tough miniaturization requirements.
As is well known, CDMA possesses such advantages as high capacity, low power transmission, and system flexibility, but it suffered from broadband occupancy of wasting finite frequency resource owing to innocent spectr...
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As is well known, CDMA possesses such advantages as high capacity, low power transmission, and system flexibility, but it suffered from broadband occupancy of wasting finite frequency resource owing to innocent spectrum spreading. Narrowing the frequency bandwidth occupied by the channels is an efficient method of developing high capacity digital transmission as one of the most important key technologies promising effective frequency usage. Narrowing the frequency bandwidth both of the primary and secondary modulation has been discussed in an effort to realize high capacity and speed diffCDMA. The phase continuity primary DQPSK, which has already been reported as a solution for 2 Mbps/8 Mcps diffCDMA, is reviewed here to realize the higher reliability and frequency efficiency of 2 Mbps/4 Mcps diffCDMA. Virtual segment interleaving is discussed as a way of reducing the chip rating as one of the important solutions for effective frequency usage without the problems of system reliability and complexity. Both continuous phase primary modulation and continuous chip shaping are also enhanced in this proposal for 2 Mbps/4 Mcps diffCDMA.
This paper presents a discrete multitone transmission system employing turbo trellis coded modulation. The combination exploits the superior performance of turbo codes on additive white Gaussian noise channels. A sing...
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This paper presents a discrete multitone transmission system employing turbo trellis coded modulation. The combination exploits the superior performance of turbo codes on additive white Gaussian noise channels. A single turbo code is used to modulate all subchannels in the multitone system. Thus, the turbo code is independent of the multitone system and channel parameters. The system can be used to achieve a significant coding gain or rate increase over an uncoded system.
In this paper a hybrid binary frequency shift keying/multiple phase shift keying (BFSK/MPSK) modulation technique employing generalised array codes (GAC) and trellis decoding is proposed. The performances of the GAC e...
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In this paper a hybrid binary frequency shift keying/multiple phase shift keying (BFSK/MPSK) modulation technique employing generalised array codes (GAC) and trellis decoding is proposed. The performances of the GAC employing the hybrid BFSK/MPSK are compared with those employing BPSK, MPSK schemes and the corresponding uncoded MPSK scheme.
In this paper, a communication scheme based on Gaussian minimum shift keying (GMSK) signal with trellis-coded modulation is presented. The coded/modulation scheme is an attractive technique for transmission of digital...
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In this paper, a communication scheme based on Gaussian minimum shift keying (GMSK) signal with trellis-coded modulation is presented. The coded/modulation scheme is an attractive technique for transmission of digital information over a bandwidth and power-limited channel. The coding gain of trellis codes provides power efficiency, and GMSK provides bandwidth efficiency due to the constant-envelope properties and good spectral features like all the CPM signals. In the receiver we propose an optimum detection Viterbi algorithm. Optimal trellis codes for the scheme can be found with computer simulation.
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