1,720,967 research outputs found
Log-likelihood ratio (LLR) conversion schemes in orthogonal code hopping multiplexing
No full textLog-likelihood ratio (LLR) conversion schemes are proposed to reduce the effect of perforations that occur in orthogonal code hopping multiplexing (OCHM), which was previously proposed to accommodate more downlink channels than the number of orthogonal codewords. The proposed LLR conversion schemes greatly reduce the required signal-to-noise ratio (SNR) in channel decoding even when the perforation probability is high. The performance of the proposed schemes is evaluated by simulation in terms of the required E-b/N-0 for a 1% block error rate
Performance Comparison of Orthogonal Code Hopping Multiplexing(OCHM) and HDR Schemes in Synchronous Downlink
No full textCollision mitigation by log-likelihood ratio (LLR) conversion in orthogonal code-hopping multiplexing
Full text linkLog-likelihood ratio (LLR) conversion schemes are proposed to mitigate the effect of collisions (or perforations) that occur in orthogonal code-hopping multiplexing (OCHM), which was previously proposed to accommodate more downlink channels than the number of orthogonal codewords. The proposed LLR conversion schemes greatly reduce the required SNR in channel decoding even when the perforation probability is high. The perforation probability in some LLR conversion schemes is estimated and several estimation methods are proposed. An LLR conversion scheme without estimation of the perforation probability is also proposed to avoid accurate estimation. The performance of the proposed schemes is evaluated by simulation in terms of the required E-b/N-0 for a 1% block error rate (BLER).This work was supported by Korea
Research Foundation Grant (KRF-2002-908-D00036)
Mobility modeling and traffic analysis in three-dimensional high-rise building environments
No full textTo efficiently plan future personal communications services, we need to solve various mobility/traffic problems in one dimensional (1-D), two-dimensional (2-D), and three-dimensional (3-D) micro- or pico-cell environments. Although many users exhibit vertical motion inside elevators in high-rise buildings, there have been no studies regarding cell planning which take into account vertical motion with elevators, In this paper, we extend the previous 3-D indoor mobility modeling by considering the proper boundary conditions on each floor and vertical motions through elevators and modeling mobility in high-rise buildings in order to estimate the number of handoffs, We then propose a blocking probability model with mobility as a traffic model in 3-D indoor environments, Using this model, we can obtain the required number of channels per cell under the given blocking probability constraint. These results can be used in planning the networks of future personal communications services
High reuse efficiency of radio resources in urban microcellular systems
No full textA new microcell configuration scheme in urban areas is proposed in order to increase the reuse efficiency of radio resources. Multiple directional-beam antennas lined up along a street form a cigar-shaped cell. Antennas are located at intersection and are directed along the intersecting streets. Two antennas facing each other Form a microzone and, therefore, a cigar-shaped cell consists of multiple microzones in a line. Each microzone is protected against cochannel interference from neighboring microzones by confinement of transmitted signals to a microzone using down-tilting of antenna beams. Therefore, a radio channel which is occupied in one microzone can be used in adjacent microzones. An increase in system rapacity is achieved by the high reuse efficiency of radio resources. The proposed system increases system capacity up to 560% with a call blocking probability of 1% when compared with a conventional system. In addition, a macrodiversity scheme using two antennas in a microzone improves call quality on reverse link
Determining the Optimal Threshold Values of MCS Levels for Retransmission Packets in HARQ Schemes
No full textSimulator on the WCDMA High Speed Downlink Packet Access System and Performance Evaluation of a Multiplexing Scheme with Hybrid Schedulers
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