• Journal of the Korea Institute of Military Science and Technology
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• v.16 no.3
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• pp.322-331
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• 2013

Wireless Mesh Networks(WMNs) is generally composed of radio nodes in the mesh topology. WMNs consists of mesh client, mesh router and gateway connected to a wired network. Each client and router relay messages to the gateway for communication. WMNs is widely used recently in many areas can provide extended coverage based on multi-hop communication and ubiquitous communication at any time and any location. However the competition and collision between each node to transmit data is inevitable when the same channel is used for transmission. The transmission opportunities and the throughput of nodes located far from gateway decrease more if the communication channel is accessed based on competitive CSMA/CA scheme using DCF(Distributed Coordination Function) provided by IEEE 802.11 MAC. In this paper, we improve the performance of the TCP fairness and throughput of the nodes with more than 2 hops by applying various algorithms for controlling contention window values. Also, we evaluate the performance using ns-2 simulator, According to the results, proposed scheme can enhance the fairness characteristic of each node irrespective of data to the gateway.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.8
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• pp.1770-1785
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• 2013

In this paper, a multi-hop transmission protocol based on parallel communication of secondary users (SUs) is proposed. The primary multi-hop network coexists with a set of SUs by cooperative spectrum sharing. The main optimization target of our protocol is the overall performance of the secondary system with the guarantee of the primary outage performance. The energy consumption of the primary system is reduced by the cooperation of SUs. The aim of the primary source is to communicate with the primary destination via a number of primary relays. SUs may serve as extra decode-and-forward relays for the primary network. When an SU acts as a relay for a primary user (PU), some other SUs that satisfy the condition for parallel communication are selected to simultaneously access the primary spectrum for secondary transmissions. For the proposed protocol, two opportunistic routing strategies are proposed, and a search algorithm to select the SUs for parallel communication is described. The throughput of the SUs and the PU is illustrated. Numerical results demonstrate that the average throughput of the SUs is greatly improved, and the end-to-end throughput of the PU is slightly increased in the proposed protocol when there are more than seven SUs.

• Journal of Digital Contents Society
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• v.14 no.2
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• pp.191-197
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• 2013

To complete the "anywhere" mobile service there should not be shaded areas. However, it is never economical to deploy BS's (Base Stations) in a low population density area due to the low resource utilization. We propose a design technique to install RS's(Relay Stations) which are cheaper than BS's and find the condition in which the proposed technique is acceptible. The proposed design technique aims to allocate the frequency and time resources to RS's to minimize the transmission rate degradation due to interferences between RS's as well as to maximize the parallelism in transmission. We showed by simulation that the proposed technique achieves cost benefits when the expected traffic is less than 20.32 percent of the total BS capacity. The proposed technique is compatible with the IEEE 802.16j, thus can be extended to multi-hop configuration.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.4B
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• pp.422-428
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• 2011

In this paper, we introduce system and channel modeling for an underwater ad hoc acoustic network with n regularly located nodes， and then analyze capacity scaling laws based on the model. A narrow-band model is assumed where the carrier frequency is allowed to scale as a function of n. In the network, we characterize in attenuation parameter that depends on the frequency scaling as well as the transmission distance. A cut-set upper bound on the throughput scaling is then derived in extended networks having unit node density. Our result indicates that the upper bound is inversely proportional to the attenuation parameter, thus resulting in a power-limited network. Furthermore, we describe an achievable scheme based on the simple nearest-neighbor multi-hop (MH) transmission. It is shown under extended networks that the MH scheme is order-optimal for all the operating regimes expressed as functions of the attenuation parameter.

• Journal of the Korea Institute of Military Science and Technology
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• v.23 no.4
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• pp.371-380
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• 2020

Video is principal information that facilitates commander's immediate command decision. Due to fading characteristics of radio link, however, it is difficult to stably transmit video in a multi-hop wireless environment. In this paper, we propose a MANET structure composed of a link adaptive routing protocol and a TDMA MAC protocol to stably transmit video traffic in a ultra-narrowband video streaming network. The routing protocol can adapt to link state change and select a stable route. The TDMA protocol enables collision-free video transmission to a destination using multi-hop dynamic resource allocation. As a result of simulation, the proposed MANET structure shows better video transmission performance than proposed MANET structure without link quality adaption, AODV with CSMA/CA, and OLSR with CSMA/CA structures.

• Journal of Korea Multimedia Society
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• v.12 no.9
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• pp.1273-1287
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• 2009

PEGASIS, a chain-based protocol, forms chains from sensor nodes so that each node transmits and receives from a neighbor. In this way, only one node (known as a HEAD) is selected from that chain to transmit to the sink. Although PEGASIS is able to balance the workload among all of the nodes by selecting the HEAD node in turn, a considerable amount of energy may be wasted when nodes which are far away from sink node act as the HEAD. In this study, DERP (Distance-based Energy-efficient Routing Protocol) is proposed to address this problem. DERP is a chain-based protocol that improves the greedy-algorithm in PEGASIS by taking into account the distance from the HEAD to the sink node. The main idea of DERP is to adopt a pre-HEAD (P-HD) to distribute the energy load evenly among sensor nodes. In addition, to scale DERP to a large network, it can be extended to a multi-hop clustering protocol by selecting a "relay node" according to the distance between the P-HD and SINK. Analysis and simulation studies of DERP show that it consumes up to 80% less energy, and has less of a transmission delay compared to PEGASIS.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.8 no.5
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• pp.113-119
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• 2008

Conventional 1-1-1 cooperative protocol offers path-loss gain as advantage of multi-hop and spatial diversity which is equivalent to MIMO system. This protocol is enable to get higher reliability and reduction of power consumption than those of the single-hop or multi-hop. But the 1-1-1 cooperative protocol get only the diversity order 2 and limited path-loss reduction gain because this protocol has a single cooperative relay. We propose 1-2-1 cooperative protocol using two cooperative relays R1, R2. The 1-2-1 cooperative protocol can improve path-loss reduction and increase diversity order 3. Moreover, the cooperative relay R2 attains diversity order 2. The signaling method in transmission uses DF (Decode and Forward) or DR (Decode and Reencode) and 1-2-1 DF/DR cooperative protocol are applied to clustering based wireless sensor networks (WSNs). Simulations are performed to evaluate the performance of the protocols under Rayleigh fading channel plus AWGN (Additive White Gaussian Noise).

• The Journal of the Korea Contents Association
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• v.18 no.3
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• pp.611-625
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• 2018

With innovative advances in wireless communication technology, many researches for extending network lifetime in maximum by using energy harvesting have been actively performed on the area of network resource optimization, QoS-guaranteed transmission, energy-intelligent routing and etc. As known well, it is very hard to guarantee end-to-end network delay due to uncertainty of the amount of harvested energy in multi-hop RF(radio frequency) energy harvesting wireless networks. To minimize end-to-end delay in multi-hop RF energy harvesting networks, this paper proposes an energy efficient routing metric based on interference aware and protocol which takes account of various delays caused by co-channel interference, energy harvesting time and queuing in a relay node. The proposed method maximizes end-to-end throughput by performing avoidance of packet congestion causing load unbalance, reduction of waiting time due to exhaustion of energy and restraint of delay time from co-channel interference. Finally simulation results using ns-3 simulator show that the proposed method outperforms existing methods in respect of throughput, end-to-end delay and energy consumption.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.9A
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• pp.801-808
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• 2011

We propose MBAP(Multi-rate Broadcast Active Probing) technique to get the right measurements for link quality in Wireless Mesh Network (WMN). Most routing protocols for WMN make use of link quality-aware routing metrics, such as ETX(Expected Transmission Count) and ETT(Expected Transmission Time), while the hop count is usually used in MANET (Mobile Ad-hoc NETwork). A broadcast based active proving technique is adopted in the previous studies to get the ETX or ETT of a link. However this technique does not reflect the multi-rate feature of WLAN because it uses a single fixed transmission rate for broadcast which usually differs from the actual rate used in data transmissions. MBAP overcomes this shortage by exploiting various rate broadcast frames for probing. We implement MBAP on linux system by modifying WLAN driver and related kernel sub-systems. Experimental results show that MBAP can capture link quality more accurately than the existing techniques.

• Journal of information and communication convergence engineering
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• v.8 no.2
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• pp.223-227
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• 2010

In this paper, we present a QoS-aware MAC protocol (QA-MAC) for cluster based wireless sensor networks (WSNs). QA-MAC is a TDMA-based scheduling protocol that minimizes the energy consumption in multi-hop WSNs and provides Quality of Service (QoS). A dynamic scheduling algorithm according to the number of member nodes, node traffics, and traffic priorities is suggested. The selected cluster head allocates time slots for all member nodes in the first TDMA schedule period of each round. During the second schedule period in each round, the cluster head makes a schedule for all data transmission. The proposed QA-MAC (QoS-Aware MAC) could save energy, reduce transmission delay, and support QoS.