This paper addresses power saving for STAs (Wireless Stations) in WLANs (Wireless LANs). Mobile devices are increasingly used in situations in which they access WLANs. However, mobile devices consume large amounts of power when they communicate through a WLAN, and this shortens their battery lifetime. IEEE 802.11 specifies PSM (Power-Saving Mode) as the power-saving method for standard WLANs. However, the sleep conditions specified by PSM for STAs are not optimal in terms of power saving, except when the number of STAs is small, and this increases packet transfer delay. In this paper, we propose a power-saving method in which STAs reduce power consumption by sleeping for a period specified by the NAV (Network Allocation Vector) duration, which is set by an RTS/CTS handshake, and the duration of the NAV is extended by bidirectional burst transmission. To suppress the transfer delay caused by the bidirectional burst transmission, an AP (Access Point) manages the transmission deadline of each downlink packet on the basis of its acceptable value of delay and adapts the number of packets transferred in the bidirectional burst transmission. Although another existing method also uses the NAV duration to manage STA sleeping, the bidirectional burst transmission can only be initiated by the STAs themselves and the NAV is of an extremely limited duration. On the other hand, the proposed method specifies generalized bidirectional burst transmission without the limitations of the transmission initiator and the burst length within acceptable packet transfer delay. Moreover, we investigate the combination of the proposed method with PSM in order to improve the performance in situations in which the number of STAs is small by taking advantage of the combined properties of PSM and the proposed method. The evaluation results demonstrate that these proposed methods can reduce the power consumption of wireless stations and suppress packet transfer delay.

The traffic of the future aggregation network will dynamically change not only in volume but also destination to support the application of virtualization technology to network edge equipment to achieve cost-effectiveness. Therefore, future aggregation network will have to accommodate this traffic cost-effectively, despite dynamic changes in both volume and destination. To correspond to this trend, in this paper, we propose an optical layer 2 switch network based on bufferless optical time division multiplexing (TDM) and dynamic bandwidth allocation to achieve a future aggregation network cost-effectively. We show here that our proposed network architecture effectively reduced the number of wavelengths and optical interfaces by application of bufferless optical TDM technology and dynamic bandwidth allocation to the aggregation network.

Multi-Channel MAC protocols increase network throughput because multiple data transmissions can take place simultaneously. However, existing Multi-Channel MAC protocols do not take full advantage of the multi-channel environment, because they lack a mechanism allowing wireless stations to acquire vacant channel and time resources. In this paper, we first establish the basic model of existing Multi-Channel MAC protocols to know the capability of the most important existing protocols. Next, under the condition that each station can use only two transceivers, we propose Multi-Channel MAC protocols that effectively utilize idle channels and potentially available time resources of stations by employing bursts and interrupted frame transfers. We assume a transceiver can behave as either a transmitter or a receiver but not both at the same time. Moreover, we show the effectiveness of our proposal by computer simulation. Furthermore, through the evaluation in the case that each station can use more than two transceivers, we confirm two transceivers' case is best solution in terms of both attained throughput and hardware complexity.

We present a predictive closed-loop power control scheme for delay-prone burst transmission systems. The scheme has a sample-by-sample predictor compensating burst delay and a built-in channel encoder reducing power control command bit error.

We present a case of design and implementation of a high-speed burst QPSK (Quaternary Phase Shift Keying) receiver. Since the PSK modulation carries its information through the phase, the baseband digital receiver can recover transmitted symbol from the received phase. The implemented receiver estimates symbol time and frequency offset using sampled data over 32 symbols without transmitted symbol information, and embedded RAM is used for received phase delay over estimation time. The receiver is implemented using about 92,000 gates of Samsung KG75 SOG library which uses 0.65 µm CMOS technology. The fabricated chip test result shows that the receiver operates at 40 MHz clock rate on 5.6 V, which is equivalent to the 40 Mbps data rate.

In recent years, there has been a rapid growth in applications such as World Wide Web browsing, which are characterized by fairly short sessions that transfer substantial amounts of data. Conventional connection-oriented and datagram services are not ideally engineered to handle this kind of traffic. We present a new ATM service, called Dynaflow service, in which virtual circuits are created on a burst-by-burst basis and we evaluate key aspects of its performance. We compare Dynaflow to the Fast reservation protocol (FRP) and show that Dynaflow can achieve higher overall throughput due to the elimination of reservation delays, and through the use of shared "burst-stores. " We study the queueing performance of the dynaflow switch and quantify the relationship between the loss ratio and the buffer size.