This paper proposes a new parallel high speed mobile radio transmission scheme using cyclic-shifted-codes generated from a modified M-sequence. The modified M-sequence is biased with constant direct current (dc) on an...
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This paper proposes a new parallel high speed mobile radio transmission scheme using cyclic-shifted-codes generated from a modified M-sequence. The modified M-sequence is biased with constant direct current (dc) on an M-sequence and is inserted the guard chips before and after this biased M-sequence. The proposed system has the following features: i) Orthogonality of the codes is kept not only between direct waves of each parallel channels but also between direct and delayed waves within the guard chips;ii) It is possible to reduce the number of kinds of codes allocated to one user;and iii) It is easy to recover both code and chip timings. In this paper, moreover, the performance of the proposed system was evaluated in terms of bit error rate (BER) under additive white Gaussian noise (AWGN), non-selective one path Rayleigh fading and double-spike Rayleigh fading channels. As a result, the proposed transmission scheme can transmit several Mbps in a high-speed double-spike Rayleigh fading channel with better quality in comparison with a conventional multicode CDM transmission scheme based on M-sequences.
The original DQRUMA/MC-CDMA protocol may suffer severe code collisions due to a limited number of request codes. An enhanced DQRUMA/MC-CDMA protocol using minislots for request accesses is proposed to reduce request c...
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The original DQRUMA/MC-CDMA protocol may suffer severe code collisions due to a limited number of request codes. An enhanced DQRUMA/MC-CDMA protocol using minislots for request accesses is proposed to reduce request collisions. In the proposed protocol, request attempts are transmitted concurrently with data packets of other calls. A random scheme (Scheme I) and a designated scheme (Scheme II) are distinguished depending on the methods which select a request code and a request minislot based on a lattice pool for request accesses (LPRA). Both schemes yield low request access delays due to few or no collisions during request accesses. In Scheme I one of request minislots is selected with a randomly chosen code, while in Scheme II the minislot and the code uniquely used in request attempts can resolve a code collision problem during request accesses. The performance of the proposed protocol is evaluated by simulation and the result shows that the proposed protocol outperforms the original DQRUMA/MC-CDMA protocol in terms of average total delay.
Forts novel multiplexing techniques (VSM, PSM RPM, OIM) of an optical multimedia CDMA system haw been proposed by using prime codes with different code lengths. PSM and VSM have the advantages of easily adding and con...
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Forts novel multiplexing techniques (VSM, PSM RPM, OIM) of an optical multimedia CDMA system haw been proposed by using prime codes with different code lengths. PSM and VSM have the advantages of easily adding and controlling the inserting code system, brit with a limited successful number. RPM can dynamically add the inserting codes into the original codes at the price of a complicated algorithm and lower multiplexing speed. For example, VSM, PSM, RPM, and OIM can insert the number of inserting P3-code to be 2, 3, 4, and 15 into the simultaneous number of original P7-code being 7 with the successful number of 10 for the original P7-code system. So OIM is the best model to process the multimedia CDMA system. (C) 1999 John Wiley & Sons, Inc.
In this paper, we propose a novel structure using different code system division multiple access (DCSDMA) for an optical communication system and a design algorithm to increase the system capacity. This DCSDMA system ...
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In this paper, we propose a novel structure using different code system division multiple access (DCSDMA) for an optical communication system and a design algorithm to increase the system capacity. This DCSDMA system can transmit two kinds of code systems (for example, the prime code of 7 and 3, respectively). This multicode architecture can improve the theoretical system capacity from P-7(2) to P-7(2) + 5 * p(3)(2). In this paper, we propose an optimal design method lo find the simultaneous capacity X% * 7(2) + Y% * 5 * 3(2). X% and Y% are the successful percentages determined by the simulation results. (C) 1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 21: 291-295, 1999.
Recently portable computers and mobile communications have been developed rapidly. Along with the developments of mobile computing environment, the demands of transmitting images over wireless channels are growing. Ho...
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Recently portable computers and mobile communications have been developed rapidly. Along with the developments of mobile computing environment, the demands of transmitting images over wireless channels are growing. However, high efficiency image coding techniques are not designed for the wireless communication channels. The use of variable length codes (VLCs) in those coding techniques makes a receiver hard to synchronize with the codewords on the noisy channel. On the other hand, a variable length code transmission technique utilizing multicode CDM (Code Division Multiplex) has been proposed. In this paper, the multicode CDM technique is applied to wireless transmission of images compressed by the H.263 algorithm. Especially, the proposed technique is employed for motion vector transmission. In consequence, the proposed transmission technique reduces the required E-b/N-o as compared with the conventional transmission technique.
For efficient code sharing among users, a wireless medium access control (MAC) protocol for CDMA networks is proposed, which supports connection-oriented, as well as connectionless, services and provides the various b...
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For efficient code sharing among users, a wireless medium access control (MAC) protocol for CDMA networks is proposed, which supports connection-oriented, as well as connectionless, services and provides the various bit rates needed for the integrated multimedia services. The proposed MAC protocol allows mobile terminals to use multiple slots and spreading codes bused on contention and reservation. Optimum frequency resources are allocated to the connection-oriented and connectionless services with various bit rates. Waiting and response times in the first contention are reduced, and the overall mean delay time is typically minimized in the case of connectionless bulky traffic.
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