Research On Duplex Technique Adapted To Asymmetric Transmission

With the development of communication technology, a greater and greater variety of mobile communication services turn up, and the high date rate traffics play more and more important part in future communication system, which have strong asymmetric characteristic between the uplink (UL) and downlink (DL) data rate. Furthermore, with increase of data rate, the transmission power is also enhanced and the impact on human and environment is growing. By calculation it shows that: under the restriction of electromagnetic radiation, the uplink transmission rate is easily limited, while the downlink rate has much margin, which can be much higher than the uplink transmission rate.Duplex technology is the way to achieve the resource allocation between UL and DL. Existing duplex schemes in present mobile communication systems include frequency division duplexing (FDD) and time division duplexing (TDD). In FDD scheme, the UL and DL signals are transmitted using different frequency bands, which are separated by a guard band. Meanwhile, in TDD scheme, the UL and DL signals are transmitted over the same frequency band but different time slots. TDD scheme has the advantage of flexibly adjusting UL and DL bandwidth by allocating different numbers of time slots. Yet, the crossed timeslot interference problem is very severe.To adapt to the asymmetric characteristic of future communication system, this paper has been analyzed and researched on relative asymmetry-adptive FDD technique. A novel asymmetric frequency division duplex (AFDD) is proposed, which can dynamically allocate the frequency points use according to the actual service circumstance. On this condition, the frequency distance between the matched UL and DL frequency points is also dynamically changing, and probably interference each other because of low frequency distance.Therefor, this paper proposes a duplex frequency-pair matching scheme based on dynamic frequency mapping, which can achieve flexible frequency-pair matching, and provide much more frequency-pairs which are met the separation requirement. It can well meet the service diversity and asymmetric characteristics. Furthermore, this paper establishes a model of frequency-pair dynamically matching. From the analysis it can see that: compared with FDD system, AFDD has great advantages, which can improve the frequency use ratio, decrease the new users' block probability, and enhance the system robustness.