This paper presents a physical and MAC layer analysis of the recently introduced IEEE 802.15.3c standard for multi Gbps communication at 60 GHz. We find the optimal beamwidth of the transmitting antenna, achieving a trade-off between the Piconet Coordinator discovery and the duration of the contention access period (CAP) of the IEEE 802.15.3c MAC superframe. To find the optimal beamwidth, we first analyze the link budget of 60 GHz based directional communication, to identify the transmitting and receiving antenna gain, and hence the minimum beamwidth required to achieve a specific bit error probability (BEP) for a given distance between transmitter and receiver. We introduce a more efficient method for analytically modeling the binary exponential backoff (BEB) process during the CSMA/CA based CAP of the superframe, using a 1-dimentional Markov chain. Numerical results for the required antenna gain and optimal beamwidth, demonstrate the usefulness of our analysis technique.

In order to realize very high throughput wireless local area network (WLAN) systems, which demand multi Gbps capacities/bitrates, the IEEE802.11.TGad (Next generation WLAN standard at 60GHz band) is in the standardization process. To evaluate and select the proposed physical layer modulation and coding schemes in the standardization process, channel models for each specified usage model are required. In this paper, suitable impulse channel models for that purpose are proposed. Propagation measurements are carried out in a living room environment in the 60GHz band. To cover various usage cases, line-of-sight (LOS) and non-line-of-site (NLOS) scenarios and three different signal transmission polarization types are examined, and each channel model's parameters are extracted by statistical analysis. These channel models are useful in designing systems for millimeter-wave wireless communications.

In order to clarify the dual antenna offset channel model needed to transmit multi gigabit/sec streams with directional Tx and Rx antennas at 60 GHz, the paper describes the measurement results of vertical, horizontal and circular polarized signal transmission using co-polarized and cross-polarized directional antennas. Measurement results show that the number of strong reflection waves depends on the polarization type and that the power of cross-polarized wave transmission is very small. These results are useful for developing the novel indoor millimeter-wave channel model that considers AoD, AoA and polarization type.

In this paper, we propose a deflection routing scheme for throughput improvement to realize Gbps millimeter-wave wireless personal area network (mmWave WPAN) system. The upcoming mmWave WPAN system is designed to support transmission of uncompressed high definition TV (HDTV), high speed wireless downloading and docking etc. These data-rate-greedy applications require Gbps-order throughput which can be met by the capability of mmWave PHY. However, because of the ad-hoc formed network topology, it is easily happening that the line-of-sight (LOS) path may be blocked, while the non-line-of-sight (NLOS) path is not sufficient to guarantee Gbps throughput due to signal degradation. In this paper, we propose a cross-layer deflection routing (DR) scheme to solve the issue. When the direct path is blocked, the source device finds a relay to form deflection route, send the data to the destination through this alternative route. To avoid throughput degradation due to the consumption of extra time for relay operation, the deflection route is designed to share time slots with other transmissions on direct path. Two routing algorithms are proposed, namely random fit DR (RFDR) and best fit DR (BFDR). They search appropriate relay and time slots that provides sufficient isolation of co-channel interference (CCI) between the transmissions on direct path and deflection route. Computer simulations show that, in realistic 60 GHz environment, Gbps-order system throughput is achieved under blocking condition. There is up to 35% system throughput improvement compared to the conventional relay scheme.

In order to realize intra-car multimedia communications systems composed of entertainment which requires several hundred Mbps to 1 Gbps capacity and monitoring signal transmission between many parts of the car which requires high reliability and low latency, this paper proposes a millimeter wave system which has high capacity and low latency transmission capability. To clarify the feasibility of millimeter wave systems applications to intra-car multimedia communications, propagation characteristics inside a car have been extensively measured and analyzed. The proposed system sets a car navigator as the center of Intra-car multimedia communications with an Omni antenna and receivers are assumed at front seats, back seats and the luggage space behind the back seats in a typical SUV (Sports Utility Vehicle). The measured results show i. Front seat communications are no worry with simple single carrier (SC) modems without any equalizer, ii. Back seats communications may need beam forming capability for better receive signal power (an Omni antenna system still works with a simple SC modem with a simple rake receiver but without any equalizer, iii. "Luggage space communications may require a directive / beam forming antenna for better receive signal power. The maximum delay spread observed is 6 to 7 ns and no equalizer necessity has been found for Omni antenna receivers inside a car. Further advancement to beam forming antenna will have only 1 - 2 ns maximum delay spread inside a car. Thus, this paper has proved the feasibility of millimeter wave intra-car multimedia communications system by employing a simple single carrier modem without any equalizers but with simple rake receivers.

In this paper, we propose a cross-layer deflect routing scheme that improves effective throughput of multi-hop millimeter-wave wireless personal area network (mmWave WPAN) system. The upcoming mmWave WPAN is designed to provide Gbps-order transmission capability, targeting applications like high definition TV (HDTV) transmission, high speed wireless docking and gaming etc. Adopting multi-hop relay offers solutions to the issues existing in mmWave WPAN system such as limited coverage range caused by the significant path loss, dramatic communication link change due to the unexpected blockage of the line-of-sight (LOS) path etc. However, multi-hop relay on the other hand decreases the effective throughput because of the required extra time. As a result, the compromised throughput may not be able to support the above applications which are greedy for data rate. Inspired by the fact that the significant path loss of millimeter-wave environment can provide good space isolation, our proposed scheme manages to improve the multi-hop throughput by sharing time slots for relay path with direct path for other transmissions. We also propose two algorithms, namely random fit deflect routing (RFDR) and best lit deflect routing (BFDR), to find the relay path on which the interference due to time slot sharing is low enough to guarantee the concurrent transmissions. Computer simulations show that, in realistic 60 GHz environment, the effective multi-hop throughput can be improved up to 45%.

In this paper, we propose a deflection routing scheme that improves effective throughput (defined as the successfully transmitted bits over the duration between two available sequential time slots) of millimeter-wave wireless personal area network (mmWave WPAN) systems. The upcoming mmWave WPAN is based on dynamic time division multiple access (TDMA) and designed to guarantee Gbps-order transmission capability for high definition TV (HDTV) transmission, high speed wireless docking and gaming, etc. The decode-and-forward (DF) type of relay offers a simple solution to the issues of mmWave WPAN systems, such as limited coverage range and unexpected blockage. However, due to the required extra time, DF relay on the other hand decreases the effective throughput, and may not be sufficient to satisfy the requirement of the above data-rate-greedy applications. Inspired by the fact that the significant path loss of a millimeter-wave environment can provide good space isolation, we propose a deflection routing scheme to improve the effective throughput by sharing time slots for direct path with relay path. Based on the sub-exhaustive search, a routing algorithm, named as best fit deflection routing (BFDR), has been developed to find the relay path with the least interference that maximizes the system throughput. To reduce the computational complexity of the BFDR, we have also developed a sub-optimal algorithm named as random fit deflection routing (RFDR). The RFDR algorithm finds the sub-optimized relay path, where the interference may not be the least but is sufficiently low to guarantee the concurrent transmissions. Computer simulations show that, in realistic 60 GHz environments, the effective system throughput can be improved up to 28% under grid topology and 35% under random topology. RFDR achieves almost the same order of throughput improvement with only 10% of the computational complexity of BFDR.

In order to realize a vehicle area network for multimedia entertainment systems, which demand capacities of up to 1 Gbps, and vehicle control links between many parts of the car, which demand high reliability and low latency, this paper proposes a millimeter-wave system that offers high capacity and low latency transmission. Propagation measurement results show the maximum delay spread of 6 - 7 ns can be achieved with omni antennas without complicated equalizers. Feasible advances in beam forming antenna performance will reduce the maximum delay spread inside the car to only 1 - 2 ns. This paper proves that millimeter-wave vehicle area networks can support multimedia communications as well as control links by employing a basic single carrier modem with simple rake receivers; no equalization is needed.

We developed a high speed wireless LAN prototype in 5 GHz frequency band. Maximum transmission rate of the developed WLAN system is 324 Mbit/sec using 6 multi-channels of the IEEE802.11a. We propose a SINR estimation scheme using the correlation of long training fields, and implemented it in closed-loop link adaptation. We compared the proposed link adaptation schemes with the legacy ACK-based link adaptation schemes by computerized simulation. It was found that the performances of legacy ACK-based link adaptation schemes depended largely on the parameter choices. The proposed link adaptation scheme achieved higher throughput than the legacy ACK-based link adaptation schemes. We also found that the proposed link adaptation scheme selected the optimal MCS on the developed WLAN system in both AWGN and fading conditions.

High speed wireless LAN prototype of 324 Mbit/sec has been developed. Six channel binding of 802.11 a signal on frequency domain was employed for increasing PHY data rate. Frame aggregation was employed to improve MAC-SAP throughput. Individual adaptive data rate setting on each channel, so called adaptive dynamic channel assign was implemented in order to achieve maximum MAC-SAP throughput at any channel condition. In this paper, multiple channel interleaving over all frequency channels for randomization of burst error was presented. Interleaving can be carried out over all channels or inside individual channel. Bit and packet error rate were measured using implemented WLAN equipements with/without multiple channel interleaving. It was confirmed that improvement using multiple channel interleaving were measured to be 2 dB.

We developed a high speed wireless LAN prototype in the 5GHz band. Maximum transmission rate of the developed WLAN equipment was 324Mbit/sec using 6 multi-channels of 802.11a (1). We implemented a frame aggregation scheme to improve MAC efficiency (2-3). The evaluated system throughput was achieved more than 170Mbit/sec using the implemented frame aggregation. The HDTV transmission using 324Mbit/sec WLAN equipment was demonstrated. We compared the developed prototype and the conventional 802.11g (4).

We have proposed a high-speed and large-capacity radio frequency identification (RFID) inventory method combining frame slotted ALOHA and binary tree. For the rapid inventory of a large number of tags, 1-bit flags are used as tag existence confirmation in the proposed method. The inventory time performance with erroneous 1-bit flags was evaluated. In the case of less than 100 tags and 1-bit flag error rate of less than 0.01, the degradation of the whole inventory time from the error free condition was less than 7.7%. We have compared the inventory time between the proposed method and the conventional standards. In the case of less than 100 tags, the whole inventory time of the proposed method was 2.4 ~ 15 times faster than that of the conventional standards.

To achieve ultra high speed (several gigabits/s) transmission over 60 GHz system efficiently, this paper proposes Automatic Device Discover (ADD) and frame aggregation. The computer simulation results show good feasibility of handling directional antenna for ultra high speed transmission and highly efficient transmission up to 87 percent over 4.094 Gbps PHY-SAP with 8PSK modulation.

We developed a high speed wireless LAN prototype in the 5 GHz band. Maximum transmission rate of the developed WLAN system is 324 Mbit/sec using 6 multi-channels of 802.11a. We propose a closed-loop link adaptation scheme to improve MAC efficiency. The proposed scheme inserts MCS (Modulation and Coding Scheme) feedback information into Data frame and ACK frame. The MCS is calculated based on the estimated SNR. We compared the proposed link adaptation scheme with the legacy ACK-based link adaptation schemes by computerized simulation. The proposed link adaptation scheme achieved higher throughput than the legacy ACK-based link adaptation scheme. We also found that the proposed link adaptation scheme selected the optimal MCS on the developed WLAN system.

We propose a multi-carrier transmission with constant envelope modulation for a 2Gbps wireless system using the 60 GHz band. All sub-carriers are amplified individually and combined after amplification to make the sub-carrier envelope constant. Each sub-carrier spectrum is set to overlap each other to reduce the radio frequency (RF) bandwidth. In the case of 4 minimum shift keying (MSK) sub-carriers, we can get 375 MHz base band (BB) bandwidth and 1875 MHz RF bandwidth. Therefore, the spectral efficiency is 1.07 bit/s/Hz, and the Eb/No require for 10-4bit error rate (BER) is 9.5 dB.

We developed a high speed wireless LAN prototype in the 5GHz band that is backward compatible with legacy IEEE802.11a. The developed WLAN equipment has a data rate of 324Mbit/sec using 6 PHY transmission channels of 802.11a. We propose frame aggregation to improve MAC efficiency. The proposed frame aggregation features an adaptive aggregation size selection depending on wireless channel conditions and application requirements. The optimal frame aggregation size for the PHY data rate is evaluated by using computer simulation. MAC throughput as a function of aggregation size was simulated and measured. We find that high throughput of more than 170Mbit/sec was achieved using the proposed frame aggregation.

We developed a high speed wireless LAN prototype in the 5 GHz band. Maximum transmission rate of the developed WLAN equipment was 324 Mbit/sec using 6 multi-channels of 802.11a. We proposed a novel frame aggregation scheme to improve MAC efficiency. The proposed frame aggregation scheme had a feature of an adaptive aggregation size selection depending on wireless channel conditions and application requirements. Throughput performance was simulated in the case of multiple stations with the proposed frame aggregation. The evaluated system throughput was achieved more than 150 Mbit/sec in the case of 10 STAs. It is found that throughput of the developed equipment was measured to be more than 170 Mbit/sec using the proposed frame aggregation

We developed a high speed wireless LAN prototype in the 5 GHz band. The developed WLAN equipment had a data rate of 324 Mbit/sec using 6 PHY transmission channels of IEEE 802.11a. We presented the system of 324 Mbit/sec WLAN equipment focus on PHY layer using high grade FPGA devices. In this system, we proposed channels-interleave to improve characteristics of the equipment under multi-path environment. We confirmed that the effect of channels-interleave was about 2-4 dBm under a wireless condition of 324 Mbit/sec

A new carrier frequency offset compensation algorithm for packet spread-spectrum code-division multiple-access (SS-CDMA) system is proposed. For evaluation of carrier frequency offset, 11-chip Barker codes were inserted into middle and end of the information block as pilot signals. Rotation direction and rotation amount due to carrier frequency offset are detected by phase differences between a preamble and pilot signals. Using the proposed algorithm, carrier frequency offset is evaluated by single packet. The compensation can be performed under burst transmission. We have evaluated bit error rate (BER) performance of packet SS-CDMA modem with the proposed algorithm by computer simulation. Under carrier frequency offset of less than 0.3 ppm, at the BER of 10/sup -3/, the degradation from the theoretical limit was found to be less than 0.2 dB.

We have proposed an intracell uplink of a spread-spectrum code-division multiple-access (SS-CDMA) flexible wireless network based on approximately synchronized (AS) CDMA. Since the AS-CDMA has no co-channel interference, complicated transmission power control (TPC) is not required. We have evaluated bit error rate (BER) performances in cases of varying carrier frequency offset and desired-to-undesired signal ratio (DUR). Under 2-user environment on Rayleigh fading channel with 1-path profile, at the undesired signal carrier frequency offset of 0.3 ppm and the BER of 10/sup -3/, the DUR is found to be -32 dB. Thus, using the AS-CDMA with a 2-step open-loop TPC technique, the intracell uplink is available. Furthermore, the intracell uplink without TPC technique is expected using the AS-CDMA with the received signal frequency stabilized synthesizer.

We have proposed an intracell uplink of a spread-spectrum code-division multiple-access (SS-CDMA) flexible wireless network based on approximately synchronized (AS) CDMA. Since the AS-CDMA has no co-channel interference, complicated transmission power control is not required. A modem of the AS-CDMA has been designed and implemented for the Japanese 2.4 GHz industrial, scientific and medical band. Using the implemented modem, the degradation of E/sub b//N/sub 0/ from the theoretical limit is 1.0 dB at a bit error rate (BER) of 10/sup -3/. Under a 2-user environment, the degradation of carrier-to-noise ratio from the case without undesired signal is 0.5 dB at a BER of 10/sup -3/ when the desired-to-undesired signal ratio is -20.3 dB.

We have proposed an intracell reverse link of an SS-CDMA flexible wireless network based on an approximately synchronized (AS) CDMA. The AS-CDMA features no co-channel interference during a guard-chip duration. A sequence with the guard-chip duration can be designed using the pseudo periodic method and the orthogonal frequency multi-channel method. The reverse link without co-channel interference does not require the sophisticated transmission power control, which is indispensable in the conventional systems such as IS-95. The AS-CDMA modem has been designed and implemented for the Japanese 2.4 GHz SS band. An AS-CDMA sequence of length 48 is designed. The number of the orthogonal frequency multi-channel method is 2. One of the features of the implemented reverse link modem is the use of a surface-acoustic-wave convolver as a correlator for rapid synchronization. The effects of frequency offset on stability have been evaluated using computer simulation. The simulation results have shown that the degradation of E/sub b//N/sub o/ at a BER of 10/sup -4/ is 1.4 dB, when the carrier frequency offset of an undesired signal is /spl plusmn/1 ppm and the desired-undesired signal power ratio is -30 dB. In the implemented AS-CDMA reverse link modem, the measured degradation of E/sub b//N/sub 0/ has been found to be 3.0 dB at a BER of 10/sup -4/.

We have implemented a switched current matched filter (SIMF) LSI for the synchronization channel of IMT-2000. A partial correlation structure has been proposed for reducing current transfer error accumulation, which degrades correlation dynamic range. Degradation of the correlation dynamic range can be improved 1.8 dB at the current transfer error of 1%. Power consumption of 7.5 mW has been estimated with 93% current-cut. 64 chip SIMF has been fabricated using 0.8 /spl mu/m CMOS process. The correlation peaks can be clearly observed at the chip rate of 4 Mcps. 0.2-dB degradation of probability of synchronization error has been obtained.

A new compact 2.4 GHz spread spectrum (SS) modem has been implemented using a surface acoustic wave (SAW) correlator. The authors have designed and fabricated the 2.4 GHz SAW correlator on AlN/Al/sub 2/O/sub 3/ combination. Using the SAW correlator and SAW delay line at the RF front-end, the 2.4 GHz SS signal is directly demodulated to baseband data. The PN code used is the 11-chip Barker code whose rate is 22 MHz, and baseband data rate is 2 Mbps. The degradation of the measured BER from the theoretical limit is found to be less than 3 dB of E/sub b//N/sub 0/. The authors propose a time division multiplex scheme utilizing the orthogonality of the spreading PN code in the time domain. The channel multiplex is experimentally confirmed using shifted Barker codes.