• ETRI Journal
• /
• 제43권3호
• /
• pp.561-570
• /
• 2021

This paper presents master key identifier based protocol steganography (MKIPS), a new approach toward creating a covert channel within the Secure Real-time Transfer Protocol, also known as SRTP. This can be achieved using the ability of the sender of Voice-over-Internet Protocol packets to select a master key from a pre-shared list of available cryptographic keys. This list is handed to the SRTP sender and receiver by an external key management protocol during session initiation. In this work, by intelligent utilization of the master key identifier field in the SRTP packet creation process, a covert channel is created. The proposed covert channel can reach a relatively high transfer rate, and its capacity may vary based on the underlying SRTP channel properties. In comparison to existing data embedding methods in SRTP, MKIPS can convey a secret message without adding to the traffic overhead of the channel and packet loss in the destination. Additionally, the proposed covert channel is as robust as its underlying user datagram protocol channel.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제9권3호
• /
• pp.941-955
• /
• 2015

In dual-channel networks (DCNs), all frequency hopping (FH) sequences used for data channels are chosen from the original FH sequence used for the control channel by shifting different initial phases. As the number of data channels increases, the hitting frequency point problem becomes considerably serious because DCNs is non-orthogonal synchronization network and FH sequences are non-orthogonal. The increasing severity of the hitting frequency point problem consequently reduces the resource utilization efficiency. To solve this problem, we propose a novel hitting frequency point collision avoidance method, which consists of a sequence-selection strategy called sliding correlation (SC) and a collision avoidance strategy called keeping silent on hitting frequency point (KSHF). SC is used to find the optimal phase-shifted FH sequence with the minimum number of hitting frequency points for a new data channel. The hitting frequency points and their locations in this optimal sequence are also derived for KSHF according to SC strategy. In KSHF, the transceivers transmit or receive symbol information not on the hitting frequency point, but on the next frequency point during the next FH period. Analytical and simulation results demonstrate that unlike the traditional method, the proposed method can effectively reduce the number of hitting frequency points and improve the efficiency of the code resource utilization.

• 한국통신학회논문지
• /
• 제37권8B호
• /
• pp.677-686
• /
• 2012

In the presence of a high power cellular network, picocells are added to a Macro-cell layout aiming to enhance total system throughput from cell-splitting. While because of the different transmission power between macrocell and picocell, and co-channel interference challenges between the existing macrocell and the new low power node-picocell, these problems result in no substantive improvement to total system effective throughput. Some works have investigated on these problems. Pico Cell Range Expansion (CRE) technique tries to employ some methods (such as adding a bias for Pico cell RSRP) to drive to offload some UEs to camp on picocells. In this work, we propose two solution schemes (including cell selection method, channel allocation and serving process) and combine new adaptive frequency partitioning reuse scheme to improve the total system throughput. In the simulation, we evaluate the performances of heterogeneous networks for downlink transmission in terms of channel utilization per cell (pico and macro), call blocking probability, outage probability and effective throughput. The simulation results show that the call blocking probability and outage probability are reduced remarkably and the throughput is increased effectively.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제7권4호
• /
• pp.651-669
• /
• 2013

In this paper, we study a novel routing algorithm based on load balancing for multi-channel wireless mesh networks. In order to increase the network capacity and reduce the interference of transmission streams and the communication delay, on the basis of weighted cumulative expected transmission time (WCETT) routing metric this paper proposes an improved routing metric based on load balancing and channel interference (LBI_WCETT), which considers the channel interference, channel diversity, link load and the latency brought by channel switching. Meanwhile, in order to utilize the multi-channel strategy efficiently in wireless mesh networks, a new channel allocation algorithm is proposed. This channel allocation algorithm utilizes the conflict graph model and considers the initial link load estimation and the potential interference of the link to assign a channel for each link in the wireless mesh network. It also utilizes the channel utilization percentage of the virtual link in its interference range as the channel selection standard. Simulation results show that the LBI_WCETT routing metric can help increase the network capacity effectively, reduce the average end to end delay, and improve the network performance.

• International Journal of Contents
• /
• 제8권2호
• /
• pp.19-22
• /
• 2012

New and handoff calls control mechanisms are the key point to wireless cellular networks. In this paper, we present an adaptive algorithm for dynamic channel allocation scheme with guard channels and also with handoff calls waiting queue ensuring that handoff calls take priority over new calls. Our goal is to find better tradeoff between handoffs and new calls blocking probabilities in order to achieve more efficient channel utilization. Simpy is a Python based discrete event simulation system. We use Simpy to build our simulation models to get analytical data.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 1998년도 하계종합학술대회논문집
• /
• pp.74-77
• /
• 1998

We consider connection-oriented wireless cellular networks. These networks employ dedicated radio channels for the transmission of signaling information. A forward signaling channel is a common signaling channel assigned to carry the multiplexed stream of paging and channel allocation(virtual circuit allocation) packets from a base station to mobile stations. The delay levels experienced by paging and channel allocation packets have serious effect on the utilization level of the limited radio channel capacity. While a slotted mode operation is used to reduce the power consumption level at mobile stations, it may induce an increase in packet delay levels. In this paper, we thus consider a multiplexing scheme for paging and channel allocation packets under which slots are dynamically allocated for the paging packet transmission. For this dynamic scheme, we develop an analytical method for deriving the delay characteristics exhibited by paging and channel allocation packets, and investigate the effect of network parameters on the delay level by using this method.

• 한국통신학회논문지
• /
• 제31권2A호
• /
• pp.86-96
• /
• 2006

EPON은 널리 퍼져있는 이더넷(Ethernet) 기술을 사용하고, 낮은 이더넷 장비비용과 낮은 광(fiber) 기반비용을 제공하기 때문에, 광대역 고속 가입자 망에서 점점 더 매력적인 해법으로 관심을 끌고 있다. EPON에서는 서로 다른 ONU들이 데이터를 보내기 위해서 상향 채널을 공유해야 하기 때문에 상향 트래픽을 제어하는 것이 중요하다. 본 논문에서는 높은 대역폭 사용효율을 제공하며, 서비스 클래스 별로 서로 다른 QoS를 지원하는 스케줄링 알고리즘인 HUHG(High Utilization and Hybrid Granting) 알고리즘을 제안한다. 제안된 알고리즘은 고정된 EF(Expedited Forwarding) sub-cycle의 특성을 이용하여, 다음 cycle의 EF sub-cycle을 미리 할당하여 idle time을 제거 또는 줄임으로써 높은 대역폭 사용효율을 얻을 수 있을 뿐만 아니라, EF 클래스에 대한 패킷 delay와 delay variation을 최소화 할 수 있다. 본 논문에서는 제안된 알고리즘의 효과를 확인하기 위해서 기존 연구를 바탕으로 대역폭 사용효율을 분석하고, OPNET을 통한 모의실험 결과를 통해서 성능분석을 기술한다.

• 전자공학회논문지A
• /
• 제33A권2호
• /
• pp.50-58
• /
• 1996

This paper proposes the channel-access protocol suitable to a very high speed photonic WDM network with star configuration, which can provide a high channel utilization and insensitivity to the propagation delay. The proposed protocol employs a control channel and a simple status table to deal with the propagation delay which has been a major limiting factor in the performance of the very high speed optical communication networks. The control channel transmits control information in order to reserve access on data channels, and each node constitutes a status table after the reception of control pckets which holds information about the availbility of destination node and data channel. The proposed protocol is insensitive to the propagation delay time by removing necessity of the retransmission and by allowing parallel transmission of control packet and data packets. It is proved in analysis and discrete event simulation that the proposed protocol is superior in throughput and mean delay, especially at the high load conditions compared to the existing high speed channel-access protocols.

• 한국정보과학회논문지:정보통신
• /
• 제37권3호
• /
• pp.249-253
• /
• 2010

폭발적인 트래픽 양의 증가와 함께 ISM 대역과 같이 라이선스가 필요 없는 주파수 대역의 포화상태로 인하여 무선네트워크의 주파수 자원이 점점 부족해지고 있다. 그러나 반대로 라이선스 주파수 대역의 이용률은 극히 저조한 상태라는 것이 여러 실험결과를 통해 알려졌다. 이러한 라이선스 주파수의 비효율적인 측면을 완화하기 위해 최근 인지라디오 기술이 제안되고 있다. 인지라디오는 비록 라이선스가 없는 사용자라도 라이선스 사용자를 방해하지 않는 한에서 라이선스 주파수 대역을 사용할 수 있도록 하는 기술로써 라이선스 주파수 대역을 좀 더 효율적으로 사용할 수 있게 하는 기술이다. IEEE 802.22는 인지 라디오를 기반으로 하는 첫 번째 표준 무선네트워크이다. IEEE 802.22는 라이선스 사용자의 충분한 보호와 주파수 대역 사용의 효율성을 극대화 하기 위해 Two-Stage 채널 센싱 기법을 제안하고 있다. 본 논문에서는 Two-Stage 채널 센싱의 오버헤드를 분석하고 센싱에 사용되는 시간이 오버헤드에 미치는 영향을 알아보고자 한다.

• 한국식생활문화학회지
• /
• 제13권1호
• /
• pp.37-46
• /
• 1998

Distribution structure is the link between a society's needs and its industrial responses. A change in distribution structure brings about a consumption structure which may results in considerable changes in lifestyle including food habits. The purpose of this study was to evaluate a effect of change of distribution structure on the food purchase. The survey was carried from May to June, 1997 by way of questionnaire of 407 housewives, aged 23-64 years, in Seoul and the capital area. The questionaire consists of sociodemographic characteristics of the subjects and distribution channel, information route of food selection, acknowledgement and coefficient of utilization of new distribution channel, mainly used distribution channel in food purchase, important factors in food selection, and food purchasing behavior. Their data were statistically analyzed based on frequency, mean, and $X^2-test$. The major findings of this study were as follows; 1) Most frequently used distribution channels in food purchase were supermarket(38.53%), department store(15.23%), discount store(14.05%), a conventional retail market(13.87%), membership wholesale club(8.07%), and a conventional wholesale market(6.53%). 2) The new distribution channels that subjects have ever used were discount store(75.4% of the subject), membership wholesale club(63%), mail order house(32%), outlet store(29.4%), home shopping(10.3%). 3) Compared to the subject living far from the new distribution channel, the subject living close to the new distribution channel was higher in frequency of new distribution channel utilization. These observations suggest that change of the distribution structure promotes the change of the food purchasing behavior.