Wideband-CDMA radio control techniques for third-generation mobile communication systems

Onoe, S.; Ohno, K.; Yamagata, Katsuhiko; Nakamura, T.

doi:10.1109/vetec.1997.600446

Cited by 29 publications

(6 citation statements)

References 7 publications

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“…As the thirdgeneration wireless communication systems are likely to adopt synchronous CDMA [26], [27], our proposed structure may provide a possible realization, especially at the random access mode.…”

Section: Discussionmentioning

confidence: 99%

“…The optimum multiuser detection based on the MAP rule [22] is to find a data vector (select a most likely hypothesis) given the observation. If each hypothesis is equally likely, it is equivalent to maximize the likelihood function proportional to the conditional PDF (27) As depicted in (27), the computational complexity grows exponentially with the number of active users, i.e., the dimension of . Practically, for each observation interval, the detector should not have the a priori information of and .…”

Section: A Problem Formulation and Optimum Multiuser Detectionmentioning

confidence: 99%

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Identification of active users in synchronous CDMA multiuser detection

Chen

1998

IEEE J. Select. Areas Commun.

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The level of multiple access interference (MAI) in code division multiple access (CDMA) communication systems is a time-varying parameter related to the number of active users. Almost all existing multiuser detection schemes were designed based on a priori information of the active users. In many situations, however, the multiuser receiver does not know the number of active users, and the receiver designed for the detection of all users may lead to poor performance. To develop a more efficient detection scheme in practical applications, we propose a two-stage detection structure consisting of preprocessing (identification) and postprocessing (detection). In the preprocessing, we apply the subspace concept and a method based on the multiple signal classification (MUSIC) algorithm [1] to identify the active users while requiring only a priori knowledge of all of the users' signature sequences. The proposed preprocessor is shown to be asymptotically near-far resistant, and to have the ability to identify the active users in a simple and reliable way. While in the detection process, as we efficiently use the active users' information in every observation interval, the performance is clearly improved compared to the conventional structure without identification. Moreover, the effect of imperfect identification on the decorrelating detector is also extensively analyzed. Though the decorrelating detector's inherent near-far resistant characteristic is impaired by imperfect identification, the proposed structure still outperforms the conventional structure in the general near-far environment.Index Terms-Code division multiple access (CDMA), identification, multiuser detection, multiple signal classification (MU-SIC), near-far resistant.

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Section: Discussionmentioning

confidence: 99%

Section: A Problem Formulation and Optimum Multiuser Detectionmentioning

confidence: 99%

Identification of active users in synchronous CDMA multiuser detection

Chen

1998

IEEE J. Select. Areas Commun.

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“…Unfortunately, it is hard to characterize directly according to the VBR characteristics of the high-priority data in each frame of MPEG video. To overcome this difficulty, the expression of (1) can be approximated by a form in the slice manner Slice CSlice Code CATMh (2) where Slice is the average number of message bits in a slice, CSlice denotes the average number of bits in a coded slice using outer coding scheme only. Code and CATMh represent the average numbers of bits in the inner code overheads and bits in the coded ATM headers for a slice, respectively.…”

Section: A Code Selection Principle For Outer Codes According To Datmentioning

confidence: 99%

Wireless ATM-based multicode CDMA transport architecture for MPEG-2 video transmission

Chang

Lin

1999

Proc. IEEE

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In this paper, we present a generic ATM-based multicode code division multiple access (CDMA) transport architecture for the Motion Picture Experts Group phase 2 (MPEG-2 ) compressed video services over a bandlimited mobile channel with the emphasis of wireless asynchronous transfer mode (ATM) cell design, spreading code management, and the impact of CDMA systems on the video services. Such services allow users to share novel MPEG-2 video applications without any geographical restrictions. The ATM technique is especially well suited for variable bit rate (VBR) MPEG-2 video because of its ability to allocate bandwidth on demand to these services. However, since the mobile radio has a limited channel capacity, the overall capacity of the traditional ATM-based CDMA system may not be sufficient to accommodate the MPEG-2 video services requested by the multiple mobile users simultaneously. To tackle this difficulty, a multicode CDMA technique is proposed to provide multiple VBR MPEG-2 video services by varying the number of spreading codes assigned to each MPEG-2 video in order to meet its dynamic throughput requirement. Moreover, both the multipath fading and interference on CDMA radio channels tend to cause significant transmission error and MPEG-2 bit streams are very vulnerable to these errors. Powerful forward error correction (FEC) codes are therefore necessary to protect the video data so that it can be successfully transmitted at acceptable signal power levels. Two separate FEC code schemes are applied to the header and payload of an ATM cell containing MPEG-2 video data, respectively. The ATM cell header is protected by a relatively powerful FEC code to ensure the low average cell loss rate (CLR). On the other hand, the ATM cell payload is encoded for varying degrees of error protection according to both the priority and statistical behavior of the payload data in MPEG-2 videos. An adaptive FEC code combining scheme is proposed to provide the good protection for payload data with the maximization of its code rate in order to minimize the extra bandwidth for FEC overhead. Two typical MPEG-2 test sequences are conducted to evaluate the effectiveness of our system.

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“…For example, in the case that a large amount of traffic is transmitted by some flow, a channel will be dedicated to it and its packets can be efficiently transmitted over it, whereas flows with only a small amount of traffic share the common channel. Radio resources can be efficiently utilized in some adaptive way of selecting an appropriate transmission channel according to the traffic characteristics [7]. The channel selecting/switching is controlled by RNC (Radio Network Controller), and the specific scheme in RNC has not been standardized.…”

Section: Introductionmentioning

confidence: 99%

Performance Evaluation of Channel Switching Scheme for Packet Data Transmission in Radio Network Controller

Ohta

Kawahara

Ikenaga

et al. 2002

NETWORKING 2002: Networking Technologies, Services, and Protocols; Performance of Computer and Communication Networks; Mobile A

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Abstract. W-CDMA (Wideband-CDMA) is expected for the radio access technology of the third-generation mobile telecommunication systems. In the second-generation systems, voice traffic from each user has mainly been transmitted via the dedicated transport (radio) channel. In addition, the thirdgeneration systems will efficiently accommodate data traffic based on the packet transmission in the shared common transport channel. Therefore, data traffic can be transmitted via one of two types of channels: i.e., dedicated channel and common channel. However, the channel selecting/switching scheme in RNC (Radio Network Controller) has not been standardized. Thus, in the present paper, we will propose some channel switching schemes and evaluate their performance in terms of the packet loss probability and the utilization of dedicated channels by means of simulations.

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Wideband-CDMA radio control techniques for third-generation mobile communication systems

Cited by 29 publications

References 7 publications

Identification of active users in synchronous CDMA multiuser detection

Identification of active users in synchronous CDMA multiuser detection

Wireless ATM-based multicode CDMA transport architecture for MPEG-2 video transmission

Performance Evaluation of Channel Switching Scheme for Packet Data Transmission in Radio Network Controller

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