Investigation into millimeter-wave radio over fiber transmission for future high speed pico-cellular mobile communications | |
| Author | Zhou, Ming-tuo |
| Call Number | AIT DISS. no. TC-03-01 |
| Subject(s) | Millimeter wave communication systems Radio--Transmitters and transmission Mobile communication systems |
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Engineering, School of Engineering and Technology |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. TC-03-01 |
| Abstract | Pico-cellular networks operating in mm-wave bands are expected to be used for the distribution of future broadband mobile services. Such broadband systems will require an extremely large number of base stations (BS's) whose design will therefore need to be as cost effective as possible. Radio-over-fiber (ROF) systems are, in general, potential candidates that could provide both simplification of the base stations and an efficient fiber network for the connection of the base stations to the central office facilities . In particular, attractive alternatives are schemes that are capable of remotely delivering a modulated millimeter (mm) wave carrier to the base station while simultaneously producing a millimeter local-oscillator (LO) wave for the down-conversion (to an intermediate frequency) of the uplink mm-wave signal. In this work, considerably extending previous developments, we propose and report on the characteristics of three possible configurations, in ascending order of performance, that we have developed for this type of ROF transmission. The first configuration is based on the use of two dual-electrode Mach-Zehnder modulators (MZM's) in parallel. One modulator is driven by a sine wave at the mm-wave frequency (/LO) of the LO that is needed for the down conversion of the uplink mm-wave carrier. The second modulator is driven by a "sub-carrier" bearing phase-shift keyed (PSK) data, while both MZM's are configured for optical single-sideband modulation with carrier (OSSBC). Power spectra at key points in the configuration have been determined via simulations and downlink performance has been investigated through both calculations and simulations. We show that in this configuration, for a laser line width of 30 MHz and a transmitted power of 0 dBm, it is possible to transmit, without repeaters and at a bit-error rate (BER) of 10-9 , data rates of 622 Mbit/s over about 15 km of standard fiber with a chromatic dispersion of 17 ps/nm/km at 1.55 μm. With an additional optical gain compensating for the fiber loss, the link length can be increased to about 47 km for laser line width of 30 MHz, while for laser line width of 10 MHz and 50 MHz, the transmission distance becomes ~58 km and ~3 5 km, respectively. When the link length is fixed to 14 km (for a laser line width of 30 MHz) and an adjustable attenuator is inserted in the link, it is found that with 0 dBm transmitter power a BER of 10-9 can be achieved for a received optical power of -3.7 dBm. The power spectral efficiency of the first configuration is significantly improved in the second design by still driving one MZM with the sine-wave signal at/LO but by driving the second MZM with the signal at /LO upper-sideband modulated by the data-bearing subcaiTier. Calculation and simulation results show that for the same system parameters as before, the transmission distance is increased to about 51 km, or some 36 km more than in the first configuration. For laser line widths of 10 MHz and 50 MHz, link lengths of about 56 km and 40 km, respectively, become possible without additional EDF A gain (compensating for the fiber loss). Correspondingly, for a laser line width of 30 MHz, and 50 km of transmission over standard fiber, a BER of 10-9 can be achieved for a -13 dBm of received optical power, or about 9.7 dB better than in the first configuration. The third configuration offers further reduction in complexity and is based on the use of a single dual-electrode MZM, but an additional optical filter is necessary for the removal of undesired spectral components generated in this modulation fo1mat. We show that it is indeed possible to reconfigure the transmitter such that one MZM can substitute for the two MZM's used earlier, retaining the same electronic modulation scheme as before. In spite of the additional optical filter that is needed, this scheme allows further simplification of the configuration and hence reduction of its cost. Moreover, both calculations and simulations indicate no significant penalty in performance as compared to scheme two presented above. Finally, anticipating that the network configuration discussed will also rely on dense wavelength-division multiplexing or DWDM we consider the non-linear problem of fourwave mixing (FWM). This phenomenon is expected to degrade the link performance of the WDM-ROF system, particularly close to the zero-dispersion wavelength of the fiber. An effective solution for minimizing FWM crosstalk is to unequally space the optical channels such that FWM products can be generated at frequencies other than those of the optical signals. Fast allocation of unequally spaced channels (USC's), for the first time, is proposed in this study to minimize FWM crosstalk in WDM-ROF systems with OSSBC. We find that when the mm-waves carried on different wavelengths are at the same frequency, the system is partially affected by FWM crosstalk, but that many FWM components can be eliminated from the optical channels by using the proposed method. On the other hand, if the mm-wave frequencies are also allowed to be different from each other within a fixed band, the system can be made free from FWM crosstalk but at the expense of a reduced number of allowed optical channels. The existence of this trade-off offers an interesting topic for future work. |
| Year | 2003 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ;no. TC-03-01 |
| Type | Dissertation |
| School | School of Advanced Technologies (SAT) |
| Department | Department of Information and Communications Technologies (DICT) |
| Academic Program/FoS | Telecommunications (TC) |
| Chairperson(s) | Sharma, A.B.; |
| Examination Committee(s) | Ahmed, Kazi M.;Erke, Tapio J.;Kusanagi, Michiro; |
| Scholarship Donor(s) | Government of Finland; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2003 |