Time-Hopping Sequence Design for Virtual Full Duplex via Rapid On-Off-Division Duplex

To achieve virtual full-duplex(VFD)communication using half-duplex radios,the rapid on-off-division(RODD)technique has been proposed in recent years.The time-hopping(TH)sequence is critical to controlling self-interference introduced in the paradigm.By constructing the collision model with a symbol level time scale,the periodic collision correlation function properties are introduced as the performance metric for the TH sequence in the RODD system.To achieve the best VFD performance,an optimization-based method for TH sequence design is proposed.In addition,the conventional TH frame structure design for RODD system is improved.Numerical simulations are presented to demonstrate that the proposed approach can significantly increase system performance.Results indicate that the TH sequence design is very effective for the RODD system.

On Two-Tier Femtocell over Fading Environments

In this paper the system performance of an MC-CDMA (multi-carrier coded-division multiple-access) system operating over single-cell with two-tier femtocell environment is analyzed. Consider two-tier scenario is deployed with a macrocell site in which is being surrounded several femtocells, which are designed to serve a group of subscribers locate in a small coverage area such as small office, home office or a house. The coverage area is typically up to 100 meters in radius. Mostly, the femtocell is applied to serve indoor subscribers, thus, the Rayleigh fading is adopted to characterize the propagation channel. The technique of TH-MC- CDMA (time-hopped multi-carrier coded-division multiple-access) technique is supposed to transmit each symbol alternatively with fair time (slotting)/frequency (coding) for each user in the hotspots (the area around 0th femtocell). The intensity of signals estimated at a mobile unit located in the second tie, i.e., the femtocell coverage area, is an important issue. The contribution of the paper is mainly to evaluate the system performance with both the BER (bit error rate) and OP (outage probability) according to the most important parameters, for example, the activating user number, the hopping number provided by TH-MC-CDMA system and the subcarrier number. Furthermore, the discussion of interference avoidance is also discussed with non-analytically.

A 3-5 GHz TH-UWB transmitter in 0.18-μm RF CMOS technology

An RF transmitter is proposed for 3-5 GHz time-hopping ultra wideband（TH-UWB） wireless applications.The transmitter consists of a 4-GHz oscillator, a switch with a controllable attenuator and an output matching circuit.Through controlling the low frequency signals with time-hopping pulse position modulation（TH-PPM）, the circuit supplies TH-UWB signals and can directly drive an antenna by a transmission line.The transmitter was implemented in a 0.18-μm CMOS technology;the output amplitude is about 65 mV at a 50 ？ load from a 1.8-V supply, the return loss（S 11） at the output port is less than-10 dB, and the chip size is 0.7 × 0.8 mm2, with a power consumption of 12.3 mW.