The 60GHz millimeter-wave (mmWave) wireless technology is a focus of increasing attention, since its ability to transmit more than Gbps PHY data rate makes it suitable for high-speed, short-range applications such as peer-to-peer synchronization and kiosk terminals. In the case of short-range communication with a range of several tens of centimeters, only terminals present in this communication range will be affect and communication is considered to be on a one-to-one basis. In one-to-one communication, a simpler and more efficient access mechanism is preferable. The ability of current CSMA/CA based MAC, for example MAC of IEEE 802.11 WLAN systems, to achieve high throughput is limited by the low MAC efficiency caused by high signal exchange overhead, such as interframe space (IFS) and acknowledgement. This paper proposes an ACK/NACK mechanism that enhances the throughput in short-range one-to-one communication. The ACK/NACK mechanism uses Negative ACK (NACK) as the acknowledgement policy to reduce the overhead of ACK and the transmitter switches the required acknowledgement policy to ACK based on a switchover threshold. It solves a problem arising from NACK, namely, that NACK has no mechanism for keeping alive. We evaluate the throughput of the ACK/NACK mechanism by both theoretical analysis and computer simulation. The proposed ACK/NACK mechanism is implemented in 65 nm CMOS process (BBIC); we connect this BBIC to a 60 GHz RFIC and exchange frames wirelessly. In this experiment, it is verified that the ACK/NACK mechanism enhances throughput.

This paper proposes two energy-efficient standby mode algorithms in short-range one-to-one 60GHz millimeter-wave (mmWave) communications. Among the many usage scenarios for mmWave radio, file downloading from kiosk terminals or peer-to-peer sync service with portable terminals are of great interest. For these portable terminals, reducing power consumption of standby mode as well as keeping connection setup time short is important. Comparing the power consumption between frame transmission and reception in short-range one-to-one 60GHz mmWave, the power consumed for a frame reception may become larger than that for a frame transmission. The proposed two energy-efficient standby mode algorithms for one-to-one communications assure the connection setup time and take each terminal's different requirement for reduction of its power consumption into consideration. In the proposed algorithms, each terminal accesses asynchronously and operates based on an interval consisting of several sub-intervals. In one proposed algorithm (Prop 1), a terminal transmits a connection request frame (CREQ) once every sub-interval and the other terminal waits for the CREQ during one sub-interval per interval. Thus, Prop 1 reduces the power consumption for CREQ transmission. In the other proposed algorithm (Prop 2), a terminal selects one sub-interval randomly for each interval and transmits CREQs repeatedly during that sub-interval. The other terminal waits for a CREQ during this CREQ transmission period at every sub-interval. Prop 2 saves the power consumption for a CREQ reception. We evaluate the power consumption of standby mode and connection setup time for Prop 1 and Prop 2 by both numerical analysis and computer simulations. We show that the power consumption of the CREQ waiting terminal with the proposed algorithms is more than 10mW lower than that with the conventional algorithm. We also show that our numerical analysis of the proposed algorithms derives the optimum parameters and facilitates system design. Next, we implement Prop 2 in a fully-integrated CMOS transceiver chip-set with antenna, RF/analog, PHY, and MAC for 60GHz proximity wireless communication. This experimental result is the same as the analysis result and it is verified that our proposed standby algorithm works as designed.

Space division multiple access (SDMA) is an attractive technique to increase the channel capacity of wireless communication systems. In this paper, we first propose a new process to accomplish SDMA using an adaptive array at a base station receiver of broadband fixed wireless access (FWA) systems. Unlike other methods, the proposed process does not need highly accurate direction-of-arrival (DOA) estimation and is suitable to Directionally Constrained Minimization of Power (DCMP) algorithm in order to serve multiple fixed terminals. A newly modified DCMP with phase only control is proposed as well. The algorithm to control phase weights, uses only the array output power and does not require the complex baseband signals from individual array elements. The pattern measurement results in an anechoic chamber show that the proposed algorithm can direct a null to an interference while maintaining the gain to the desired signal.

Measurements of 60GHz proximity channels are performed in desktop environments with a digital camera, a laptop PC, a tablet, a smartphone, and a DVD player. The results are characterized by a statistical channel model. All measured channels are found to be similar to conventional exponential decay profiles that have a relatively large first path due to line-of-sight components. We also show that the power difference between the first path and the delay paths is related to randomization of radio wave polarization by internal reflections in the devices, whereas this is conventionally dependent on only a Rice factor. To express this effect, the conventional model is modified by adding one parameter. Computer simulations confirm that RMS delay spreads of the modeled channels are a good fit to measured channels under most conditions.

Broadband fixed wireless access (FWA) systems offer significantly higher bit rates than current cellular systems to which adaptive arrays are partly applied. Digital beam forming is being eagerly explored on account of its flexibility, but it will be difficult to apply to the high-speed systems, because its digital signal processing requires huge resources and power consumption. Conventional phased arrays, on the other hand, utilize phase shifters through RF or IF signal lines, but the phase shifters are usually both bulky and expensive. The authors propose an adaptive array steered by IF local signal phase shifters in this paper. The phase shift and the frequency shift of the signal from each antenna element can be simultaneously accomplished at the down conversion stage by the phase-controlled local signal. A prototype receiver operated in the K-band with the proposed configuration and its beam pattern measurement results are also described.