• Proceedings of the IEEK Conference
• /
• 2008.06a
• /
• pp.157-158
• /
• 2008

This paper examines an adaptive coding scheme for flat fading channels to maximize the average code rate of a coded system. The proposed adaptation technique is employed by using the required free distance of a rate compatible code depending on the channel realization. First, the system will calculate the required free distance based on the instantaneous channel gain. Based on this channel gain we will select a set of convolution code to optimize the code rate with a certain performance requirement. Simulation results show that our proposal can achieve a higher code rate.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.29 no.12C
• /
• pp.1633-1641
• /
• 2004

In satellite digital broadcasting and satellite internet, severe burst errors occur in the high-speed return channel from the satellite to mobiles. In this paper, we analyze the performance of the forward error correction (FEC) coding method in the Rayleigh fading return channel. We first investigate the channel model of Loo, LutB, Vucetic and Corazza. We then compare the performance of the convolutional, Reed-Solomon (RS), convolution-RS concatenation, and Turbo codes in rayleigh fading channel.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.25 no.3A
• /
• pp.391-398
• /
• 2000

In this paper, MRC(Maximum Ratio Combine) diversity, (23, 12) Golay code, (7, 5) Reed-Solomon code, and (3, 1) majority selection code are employed to improve the performance of DS/CDMA BRSK in Nakagami fading channel. and MRC diversity combined with other coding techniques is suggested, with which, the performance of DS/CDMA BRSK is compared and analyzed. Also, system required Eb/N0 to meet BER=10-5 for multi user data communication is obtained according to each techniques. From the results, when each techniques is employed to DS/CDMA BRSK system. coding employed system shows better performance than diversity employed system. Especially, Golay code shows better performance than oter codes. also MRC diversity is employed, the number of multiple access user to meet data communication requirement of BER=10-5 can accomodate up to 8 users. and when each code is employed, Golay code, majority selection code, and Reed-Solomon code shows the capacity of 14, 12, and 10 user respectively. But MRC diversity combined with coding techniques can reduce restriction of multiple access user. However, it is desirable these combined technique are employed according to service types and requirements provided.

• Proceedings of the IEEK Conference
• /
• 2001.06d
• /
• pp.179-182
• /
• 2001

This paper has been studied a wavelet based still image transmission over the wireless channel. EZW(Embedded Zerotree Wavelet) is an efficient and scalable wavelet based image coding technique, which provides progressive transfer of signal resulted in multi-resolution representation. It reduces therefore the reduce cost of storage media. Although EZW has many advantages, it is very sensitive on error. Because coding are performed in subband by subband, and it uses arithmetic coding which is a kind of variable length coding. Therefore only 1∼2bit error may degrade quality of the entire image. So study of error localization and recovery are required. This paper investigates the use of reversible variable length codes(RVLC) and data partitioning. RVLC are known to have a superior error recovery property due to their two-way decoding capability and data partitioning is essential to applying RVLC. In this work, we show that appropriate data partitioning length for each SNR(Signal-to-Noise Power Ratio) and error localization in wireless channel.

• Journal of KIISE:Computing Practices and Letters
• /
• v.16 no.10
• /
• pp.990-994
• /
• 2010

Mobile WiMAX does not guarantee the media qualities because it does not consider the characteristics of video coding techniques. In this paper, PC-MCA(Priority-based Combining adaptive Modulation and Coding with ARQ), a priority based channel-adaptive streaming scheme, is proposed to guarantee media qualities. PC-MCA uses QoS scheduler by scheduling priority of the media and differentially controls modulation and coding schemes according to wireless channel condition and frame priorities. It also guarantees multimedia service quality through video decoding reliability.

• Journal of Communications and Networks
• /
• v.5 no.3
• /
• pp.187-196
• /
• 2003

We consider the use of error control coding in direct sequence-code-division multiple access (OS-COMA) systems that employ multiuser detection (MUO) and space diversity. The relative performance gain between Reed-Solomon (RS) code and convolutional code (CC) is well known in [1] for the single user, additive white Gaussian noise (AWGN) channel. In this case, RS codes outperform CC's at high signal-to-noise ratios. We find that this is not the case for the multiuser interference channel mentioned above. For useful error rates, we find that soft-decision CC's to be uniformly better than RS codes when used with DS-COMA modulation in multiuser space-time channels. In our development, we use the Gaussian approximation on the interference to determine performance error bounds for systems with low number of users. Then, we check their accuracy in error rate estimation via system's simulation. These performance bounds will in turn allow us to consider a large number of users where we can estimate the gain in user-capacity due to channel coding. Lastly, the use of turbo codes is considered where it is shown that they offer a coding gain of 2.5 dB relative to soft-decision CC.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.9 no.5
• /
• pp.1682-1701
• /
• 2015

In this paper, we propose an intergraded unified imperfect CSI model and investigate the joined effects of feedback delay and channel estimation errors (CEE) for two-hop relaying systems with transmit beamforming and relay selection. We derived closed-form expressions for important performance measures including the exact analysis and lower bounds of outage probability as well as error performance. The ergodic capacity is also included with closed-form results. Furthermore, diversity and coding gains based on the asymptotic analysis at high SNRs are also presented, which are simple and concise and provide new analytical insights into the corresponding power allocation scheme. The analysis indicates that delay effect results in the coding gain loss and the diversity order loss, while CEE will merely cause the coding gain loss. Numerical results verify the theoretical analysis and illustrate the system is more sensitive to transmit beamforming delay compared with relay selection delay and also verify the superiority of optimum power allocation. We further investigate the outage loss due to the CEE and feedback delays, which indicates that the effect of the CEE is more influential at low-to-medium SNR, and then it will hand over the dominate role to the feedback delay.

• ETRI Journal
• /
• v.26 no.5
• /
• pp.375-383
• /
• 2004

This paper proposes a common interleaving method associated with independent channel-encoding among transmitter antenna branches in orthogonal frequency and code division multiplexing based on multiple-input multiple-output (MIMO) multiplexing to achieve an extremely high throughput such as 1 Gbps using a 100 MHz bandwidth. This paper also investigates the average packet error rate performance as a function of the average received signal energy per bit-to-background noise power spectrum density ratio $(E_b/N_0)$. We found that the loss in the required average received $E_b/N_0$ of the proposed method is only within approximately 0.3 dB in up to a 12-path Rayleigh fading channel, using 16QAM and Turbo coding with a coding rate of 5/6. We also clarify that even for a large fading correlation among antenna branches, 1 Gbps is still possible by increasing the transmission power. Therefore, the proposed method reduces the processing rate to 1/4 in the turbo decoder with only a slight loss in the required average received $E_b/N_0$.

• Proceedings of the IEEK Conference
• /
• 2000.06d
• /
• pp.92-97
• /
• 2000

An AMR(Adaptive Multi-Rate) speech coding algorithm has been adopted as a standard speech codec for IMT-2000. It is based on the algebraic CELP, and consists of eight speech coding modes having the bit rate from 4.75 kbit/s to 12.2 kbit/s. It also contains the VAD(Voice Activity Detector), SCR (Source Controlled Rate) operation, and error concealment scheme for robustness in a radio channel. The bit rate of AMR is changed on a frame basis depending on the channel condition. In this paper, we introduced AMR speech coding algorithm and performed the real-time implementation using TMS320C6201, i.e., a Texas Instrument's fixed-point DSP. With the ANSI C source code released from ETSI and 3GPP, we convert and optimize the program to make it run in real time using the C compiler and assembly language. It is verified that the decoded result of the implemented speech codec on the DSP is identical with the PC simulation result using ANSI C code for test sequences. Also, actual sound input/output test using microphone and speaker demonstrates its proper real-time operation without distortions or delays.

• Journal of the Institute of Electronics Engineers of Korea TE
• /
• v.42 no.1
• /
• pp.41-46
• /
• 2005

A new multiple description selective coding is proposed to overcome noisy channels. Our algorithm adopts an embedded coding scheme, in which subband coefficients are encoded one bit plane at a time using a non-adaptive arithmetic encoder. According to the importance ratio for each region, we code interest regions with more passes than background in order to reconstruct interest regions with higher quality. To overcome channel errors, we adopt multiple description scheme which adds controlled amounts of redundancy to the original data during the compression process. Proposed algorithm achieves better qualify compared with other algorithms especially in the circumstances where very low bit rate coding is required and some regions are more important than other regions.