Analysis of a Hybrid Random-Access System with Multi-User Coding (Throughput )

최근 HFC(Hybrid Fiber Coax) CATV 망이 초고속망의 하부구조로 자리를 잡아가고 있다. HFC-CATV 망의 상향채널은 가입자에서 헤드엔드로 데이터 전송시 500가입자 이상이 공유하기 때문에 충돌이 발생하게 된다. 특히, 음성, 비디오 그리고 데이터와 같은 다양한 종류의 트래픽 QoS(Qualify of Service)를 만족시키기 위해서 서비스별로 우선순위를 고려한 알고리즘이 요구되어진다. IEEE 802.14에서 제안된 우선순위 기반 3진 트리(Ternary tree)알고리즘은 정적 PNA(Priority New Access) 슬롯 구조를 가진다. 이 방법은 실시간으로 변화하는 트래픽의 요구 지연(request delay)이 높게 유지되며 서로 다른 우선순위 트래픽의 요구 경쟁 확률이 동일하다는 문제점을 가지고 있다. 따라서, 본 논문에서는 동적 PNA(Priority New Access) 슬롯 구조를 제안하여 높은 우선순위 트래픽의 요구지연을 낮게 하고 새로운 스테이션에 대해 우선순위 별로 경쟁 확률을 다르게 하는 알고리즘을 제안한다. 동일한 조건하에 두 알고리즘에 대해 요구지연 값을 비교 분석하였다. 성능 분석 결과 동적 PNA 우선순위 충돌해결알고리즘이 정적 PNA 우선순위 충돌해결알고리즘보다 낮은 요구지연을 가진다는 것을 확인할 수 있었다. Recently, the HFC-CATV network stand in a substructure of superhighway information network. Because of sharing up to 500 of subscribes, the Collision Resolution Algorithm needs in the upstream channel of HFC-CATV network. In order to provide Quality of Service (QoS) to users with real-time data such as voice, video and interactive service, the research of Collision Resolution Algorithm must include an effective priority scheme. In IEEE 802.14, the Collision Resolution Algorithm has high request delay because of static PNA(Priority New Access) slots structure and different priority traffics with the same probability. In order to resolve this problem, this paper proposed dynamic priority collision resolution algorithm with ternary tree algorithm. It has low request delay according to an increase of traffic load because high priority traffic first resolve and new traffic content with different probability. In the result of the simulation, it demonstrated that the proposed algorithm needs lower request delay than that of ternary tree algorithm with static PNA slots structure.

We consider connectionless packet switched CDMA systems where all users have to share a common bandwidth and signature sequence on a contention basis. Multiple access is achieved by the simultaneous acquisition of different users' spread spectrum transmissions. The throughput of a pure random access system of this kind suffers from acquisition errors and timing mismatches of the active users as well as instability issues. We consider schemes that use information available at the physical layer, i.e., at the output of the multiuser access detector (MUAD) designed for this random access system, to improve and stabilize the throughput. We consider timing randomization, pseudo-Bayesian stabilization and collision resolution algorithms and report the corresponding numerical results.

A low cost, high rate, single communication channel at the SOLIS

This paper considers the collision resolution algorithm when multiple packets transmit simultaneously in each slot in a non-orthogonal multiple access (NOMA) systems. Packets are divided into two groups and two different received powers can be selected. Packets in each group can select one power level as their received power. As more than one packet may transmit in a time slot in each group, collision will happen and throughput may decrease at the same time. We introduce the collision resolution period (CRP) algorithm and the collided packets will transmit in the CRP. By controlling the transmission probability in each group, we can make a big different comparing to the system without a CRP. This paper will show the optimal transmission probability and the maximum throughput. Numerical results show that our proposed algorithm yields the maximum throughput of 0.6489.

We study a binary decision fusion scheme which employs a common channel for detector-DFC communication. Unlike most parallel fusion schemes, which use a dedicated communication channel between every local detector (LD) and the data fusion center (DFC), our scheme uses a single shared, time-slotted communication link for all LDs to transmit decisions to the DFC. Two window-based methods are presented for managing traffic over this channel. The first allows simultaneous messages to collide. The DFC uses the statistics of the channel states (i.e., the number of successful transmissions, idle slots, and collisions during a specified time period) to make its global decision. The second method uses a simple collision resolution algorithm (CRA), similar to slotted-ALOHA with dynamically updated retransmission probability. With this scheme, the DFC makes its decision based on data transmitted successfully within a specified time window. Over-all performance of the systems are presented and compared. Simple rules are developed for assessing the conditions under which each one of the schemes is preferred.

In this paper we propose and evaluate several protocols for a random access channel. The channel is divided into a control subchannel which is used to inform all users of the approximate times of arrival of new packets and a data subchannel which is used to transmit the data. Packets arriving at different users at approximately the same time may cause a collision on the control subchannel. Such collisions are resolved on the data subchannel by a collision resolution algorithm. Eight protocols that differ in the feedback available on both channels and the time that the feedback is available are described and evaluated. The expected delay of each protocol is determined by modeling the system as a slotted concentrator. Comparisons are made among the protocols described and analyzed in this paper and between these protocols and other protocols that have been studied previously.

Time-of-arrival-based retransmission scheduling algorithms for unslotted ALOHA-type random access channels with high propagation delay are introduced and analysed in this paper. The techniques described are motivated by the fact that collision bursts on asynchronous channels can be analysed to create a partial time-ofarrival based ordering between the conflicting packets. Packets successfully ordered by collision burst analysis are then retransmitted in a locally synchronous, scheduled manner, thus eliminating potential further conflict between a large fraction of retransmitted messages. Collision resolution algorithms appropriate for channels with continuous signal detection, signal and collision detection, or signal and modified collision detection are described and evaluated in terms of throughput using a simple Poisson traffic model. The maximum throughput is shown to be 0.41, 0.47 and 0.509 for the three cases, thus demonstrating that the proposed time-of-arrival algorithms are competitive with the best slotted collision resolution algorithms. The practicality of the techniques described is also established by showing that maximum throughput is relatively insensitive to inaccuracies in channel feedback for a typical implementation of modified collision detection on a radio frequency channel.

A hybrid (reservation/random) medium access control protocol based on code division multiple access is described and analyzed under multimedia traffic load. The protocol meets the quality of service requirements of the different users and applications by following proper reservation policies and through a multi-priority mechanism which is embedded in its collision resolution algorithm. The priority mechanism is implemented and controlled explicitly by the users and without any involvement from the network. This makes the allocation of priority transparent to the network infrastructure and adds to the simplicity and practical value of the proposed scheme. The evaluation shows that the protocol is able to achieve high levels of utilization and is capable of supporting relatively large numbers of video/voice users and relatively high volumes of data traffic.

The IP address lookup in the communication link technologies is becoming a major bottleneck by exploring the exact matching and the parallel hashing in each prefix length. In this paper, we present an algorithm for IP address lookup and collision resolution to reduce memory space and solve collision for high speed routing based on multiple table indexing structure. Our scheme makes possible direct access in a designated IP prefix without replicating the forwarding table entries, and provides efficient collision resolution for fast route lookup with only small memory. Simulation results indicate that our algorithm provides a faster lookup than the conventional lookup schemes.

The degree of closeness in a relationship is characterized as tie strength. Estimates of tie strength can be useful in many contexts, including as a parameter in access control policies or social context based services. Several papers have proposed how tie strength can be estimated by quantifying interactions in different individual communication channels such as online social networks, phone communication and face-to-face encounters. It has been conjectured by Wiese et al. [1] that considering only a single communication channel may not lead to accurate estimates of tie strengths. In this paper, we explore this conjecture by examining whether the combination of co-location events and mobile communication data can lead to better tie strength estimations than considering each channel individually. Surprisingly, our results indicate that the conjecture may not be true, but further analysis with more extensive datasets is needed to confirm the result.

Journal Article A Phase-Based Approach for On-Chip Bus Architecture Optimization Get access Jaesung Lee, Jaesung Lee 1School of Electrical Engineering and Computer Science, Seoul National UniversitySan 56-1, Shilim-dong, Kwanak-gu, Seoul 151-742, Korea Search for other works by this author on: Oxford Academic Google Scholar Hyuk-Jae Lee, Hyuk-Jae Lee * 1School of Electrical Engineering and Computer Science, Seoul National UniversitySan 56-1, Shilim-dong, Kwanak-gu, Seoul 151-742, Korea *Corresponding author. hjlee_paper@capp.snu.ac.kr Search for other works by this author on: Oxford Academic Google Scholar Chanho Lee Chanho Lee 2School of Electronic Engineering, Soongsil University, 1, Sangdo-5-dong, Dongjak-ku, Seoul 156-743, Korea Search for other works by this author on: Oxford Academic Google Scholar The Computer Journal, Volume 52, Issue 6, August 2009, Pages 626–645, https://doi.org/10.1093/comjnl/bxn059 Published: 13 November 2008 Article history Received: 25 October 2007 Revision received: 27 August 2008 Published: 13 November 2008

Streaming media over heterogeneous lossy networks and time-varying communication channels is an active area of research. Several video coders that operate under the varying constraints of such environments have been proposed recently. Scalability has become a very desirable feature in these video coders. In this paper, we make use of a leaky-bucket rate allocation method (DBRC) that provides constant quality video under buffer constraints, and extend it in two advantageous directions. First, we present a rate control mechanism for 3D wavelet video coding using DBRC. Second, we enhance the DBRC so that it can be utilized when multiple sequences are multiplexed over a single communications channel. The goal is to allocate the capacity of the channel between sequences to achieve constant quality across all sequences.

Traditional village culture is facing severe challenges, such as the lack of inheritance subject, single communication channel, and declining attraction. Therefore, this study puts forward and implements a set of systematic digital communication strategies. Firstly, this paper constructs a digital resource library of traditional village cultural heritage by using TLS and other technical means. Then, based on the development platform such as Unity engine, users can deeply explore the village space and culture, then rely on the mainstream new media platform to spread the digital results, and finally, constantly optimize the content production and communication strategy. The experimental results show that the method in this paper shows the strong attraction of immersion technology. This paper verifies the effectiveness of digital technology in promoting the spread of traditional village culture and provides valuable data for further optimizing the communication strategy.

Transmultiplexing is a method which combines many independent digital signals into a single complex signal transmitted by a single communication channel. Properly designed, it provides perfect reconstruction of source signals from a complex signal. The data integrity is guaranteed by a set of synthesis and analysis filters banks with integer elements. Filters banks with only ‘zeros’ and ‘ones’ ensure data integrity with minimal computing power. This solution is advantageous for simple IoT systems with many sensors and 8-bit microcontrollers. The paper contains selected examples of filter banks fulfilling a perfect reconstruction for a 4-input and an 8-input transmitter with only ‘zeros’ and ‘ones’ elements. The experimental system with digital sensors (temperature) verify the method of transmultiplexing. The results of attempts to read the proper temperature value from a composite signal sample haves been provided.

Optical chaos-based communications have proven to ensure secure transmission of information at high bit rates in real operating conditions when a single message is transmitted [1]. The problem of multiplexing multiple messages on a single communication channel using chaotic cryptosystems is still under active investigation. Several schemes have been proposed for electrical and photonic systems [2,3,4]. In these schemes, multiplexing requires at least one chaotic oscillator per message transmitted both at the emission and reception. This usually leads to complex decryption.