• 디지털산업정보학회논문지
• /
• 제10권3호
• /
• pp.171-179
• /
• 2014

Among the P2P based multimedia streaming architecture, multiple chain architecture has advantage in adapting to dynamically changing network topology simply and rapidly, so this architecture is used for UCC broadcasting system. In UCC broadcasting system, general peer involved in DSLAM becomes UCC server rather than broadcasting system that transfers data from ISP servers. Therefore UCC data generated from UCC server peers is transmitted to peers through DSLAM, and this transmission uses uplink bandwidth of DSLAM. In this paper, I propose an efficient management method of DSLAM uplink bandwidths through negotiating tracker and UCC server peer or head peers of DSLAM. I propose the method that tracker restricts a bitrate of uplink stream of UCC servers when used uplink bandwidth of DSLAM exceeds a certain point of maximum uplink bandwidths. I will show the improved performance of proposed scheme rather than general method with respect to the uplink bandwidth of DSLAM by numerical analysis and simulation.

• 한국통신학회논문지
• /
• 제42권1호
• /
• pp.77-87
• /
• 2017

현재 사용되고 있는 LTE/LTE-A 이동통신망의 성능은 일반적인 무선 통신 서비스를 제공하는데 충분히 높은 대역폭과 낮은 지연시간을 제공하고 있지만, 차세대 이동통신망의 주요 서비스가 될 가상현실, 원격 제어 등의 초저지연 서비스를 지원하기 위해서는 수 ms 수준의 낮은 지연시간이 필요하다. 그러나 LTE/LTE-A 시스템에서의 상향링크 전송은 단말이 전송에 필요한 무선자원을 획득하기 위해 기지국으로부터 자원을 할당받는 스케줄링 승인 과정이 선행되어야 한다. 이 과정은 고정적인 지연시간을 가져오고, 상향링크 전송에서 낮은 지연시간을 달성하는데 걸림돌이 된다. 따라서 본 논문에서는 이러한 스케줄링 승인 과정으로 인해 발생하는 지연시간을 줄이기 위해 새로운 상향링크 전송 방법인 Cut-in 상향링크 전송방법을 제안한다. 제안하는 상향링크 전송방법의 검증을 위해 모의실험을 수행하였으며, 이 결과를 통하여 제안하는 상향링크 전송방법이 기존 LTE/LTE-A 상향링크 전송 방법보다 낮은 지연시간을 발생시킴을 보인다.

• 한국군사과학기술학회지
• /
• 제14권4호
• /
• pp.648-654
• /
• 2011

We can model marine uplink channel environment as time-correlated rician fading channel that has direct path and time varying reflected path. In this channel, error performance of uncoded system can be seriously degraded by multipath inteference. In this paper, we propose Concatenated Zigzag(CZZ) coded binary FSK signaling with noncoherent detection to improve error performance of uplink data in marine environment. CZZ code is a kind of channel coding scheme that is fast decodable as well as fast encodable. We have confirmed error performance of uplink data in marine environment can be improved dramatically through applying CZZ code.

• Journal of information and communication convergence engineering
• /
• 제10권2호
• /
• pp.117-122
• /
• 2012

We propose a hybrid multiple access (HMA) for uplink orthogonal frequency division multiple access (OFDMA) systems, which combines two resource sharing schemes: a scheduling-based resource allocation (SBRA) scheme and a contentionbased resource allocation (CBRA) scheme. The SBRA scheme is appropriate for non-real time high data rate traffic, and, CBRA is appropriate for near-real time low/medium data rate traffic. Thus, the proposed HMA scheme supports various types of traffic. As a CBRA scheme, our proposed random frequency hopping (RFH)-OFDMA scheme was presented. Simulation results show that the proposed HMA yields the best performance among various resource allocation schemes for uplink OFDMA systems.

• 한국통신학회논문지
• /
• 제38A권5호
• /
• pp.451-458
• /
• 2013

본 논문에서는 단일 주파수 이기종 셀룰러 네트워크에서 매크로셀 사용자로 인해 발생하는 간섭을 회피하여 펨토셀 상향링크 성능을 향상시키는 기법을 제안한다. 매크로셀 사용자가 펨토셀 기지국 주변에 존재할 경우 매크로셀 사용자의 송신 전력이 펨토셀에 심각한 간섭으로 영향을 주어 펨토셀 상향링크 성능이 열화된다. 이러한 문제점을 해결하기 위하여 본 논문에서는 매크로셀 사용자로 부터 극심한 간섭을 받는 펨토셀 기지국은 상하향링크 프레임 위치를 서로 변경한 뒤, 매크로셀 사용자의 데이터를 중계 기법을 통하여 매크로셀 기지국으로 전송하는 기법을 제안한다. 제안한 방식의 펨토셀 상향링크 시간 동안 펨토셀과 매크로셀 사용자가 시간을 나누어 펨토셀 기지국으로 전송하고 하향링크 시간 동안 중첩 부호화 기술을 사용하여 펨토셀 사용자와 매크로 사용자의 데이터를 동시에 전송하게 된다. 본 논문에서는 모의실험을 통하여 제안한 방식이 펨토셀 상하향링크의 성능개선에 효과가 있음을 확인할 수 있다.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제17권1호
• /
• pp.261-279
• /
• 2023

In this article, the uplink achievable rate is investigated for massive multiple-input multiple-output (MIMO) under correlated Ricean fading channel, where each base station (BS) and user are both deployed multiple antennas. Considering the availability of prior knowledge at BS, two different channel estimation approaches are adopted with and without prior knowledge. Based on these channel estimations, a two-layer decoding scheme is adopted with maximum ratio precoding as the first layer decoder and optimal second layer precoding in the second layer. Based on two aforementioned channel estimations and two-layer decoding scheme, the exact closed form expressions for uplink achievable rates are computed with and without prior knowledge, respectively. These derived expressions enable us to analyze the impacts of line-of-sight (LoS) component, two-layer decoding, data transmit power, pilot contamination, and spatially correlated Ricean fading. Then, numerical results illustrate that the system with spatially correlated Ricean fading channel is superior in terms of uplink achievable rate. Besides, it reveals that compared with the single-layer decoding, the two-layer decoding scheme can significantly improve the uplink achievable rate performance.

• Journal of Communications and Networks
• /
• 제5권2호
• /
• pp.150-156
• /
• 2003

In this paper, an uplink MC-CDMA system incorporating multiuser detection and smart antennas has been considered. The performance of asynchronous as well as synchronous system is studied over a correlated Rayleigh multipath slow fading channel. A simplified array-processing algorithm suitable for slow fading situation is investigated to overcome the heavy computational complexity associated with Eigen solutions. The effect of variable data rate in the system performance is considered and effectiveness of antenna array to handle high data rate is discussed. A brief investigation on the system performance degradation due to correlated channel is also carried out. Based on the extensive simulation carried out, the performance of the asynchronous uplink system is found dramatically improved with antenna array and multiuser detection. Asynchronicity and channel correlation are found to affect the system performance significantly. The investigated simpli- fied algorithm produces similar results as Eigen solutions in slow fading situation with much reduced complexity.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2007년도 하계종합학술대회 논문집
• /
• pp.53-54
• /
• 2007

As Cable Network is developing for 2-way high speed data service, it should be developed to transfer high speed data using limited bandwidth. If QAM is using for this, synchronization algorithms become important system parameters. In this paper, we present two methods of coarse timing recovery using CAZAC sequence for cable modem uplink.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제11권6호
• /
• pp.3012-3028
• /
• 2017

In this paper, we propose a joint power control strategy for both the uplink and downlink transmission by considering the energy requirements of the user equipments' uplink data transmissions in data and energy integrated communication networks (DEINs). In DEINs, the base station (BS) adopts the power splitting (PS) aided simultaneous wireless information and power transfer (SWIPT) technique in the downlink (DL) transmissions, while the user equipments (UEs) carry out their own uplink (UL) transmissions by exploiting the energy harvested during the BS's DL transmissions. In our DEIN model, there are M UEs served by the BS in order to fulfil both of their DL and UL transmissions. The orthogonal frequency division multiple access (OFDMA) technique is adopted for supporting the simultaneous transmissions of multiple UEs. Furthermore, a transmission frame is divided into N time slots in the medium access control (MAC) layer. The mathematical model is established for maximizing the sum-throughput of the UEs' DL transmissions and for ensuring their fairness during a single transmission frame T, respectively. In order to achieve these goals, in each transmission frame T, we optimally allocate the BS's power for each subcarrier and the PS factor for each UE during a specific time slot. The original optimisation problems are transformed into convex forms, which can be perfectly solved by convex optimisation theories. Our numerical results compare the optimal results by conceiving the objective of maximising the sum-throughput and those by conceiving the objective of maximising the fair-throughput. Furthermore, our numerical results also reveal the inherent tradeoff between the DL and the UL transmissions.

• 한국통신학회논문지
• /
• 제32권5A호
• /
• pp.417-425
• /
• 2007

하향링크 OFDMA(Orthogonal Frequency Division Multiple Access) 시스템의 경우 순환전치 구간은 지연확산만을 고려하면 되지만 상향링크 OFDMA 시스템에서는 지연확산과 함께 상향링크 신호의 타이밍 오차를 고려한 보호구간이 필요하다. 특히 셀 반경이 큰 셀에서 초기 액세스를 하는 경우, 핸드오버를 하는 경우, 오래 동안 단말이 기지국과 데이터를 주고받지 않은 경우에는 타이밍 오차가 매우 클 수 있으며 매우 큰 보호구간이 요구될 수 있다. 상향링크 OFDMA 시스템에서 작은 크기의 순환전치 구간을 유지하기 위해서는 시스템의 순환전치 구간은 그대로 둔 체 큰 타이밍 오차가 발생할 수 있는 단말의 보호구간만 증대시키는 방법이 필요하다. 이 논문에서는 상항링크 OFDMA 시스템의 보호구간을 사용자 개별적으로 확장하는 방법을 제안한다.