Telecommunications – Transmitter and receiver at separate stations – Plural transmitters or receivers
Patent
1996-08-27
1998-10-13
Crosland, Donnie L.
Telecommunications
Transmitter and receiver at separate stations
Plural transmitters or receivers
455524, 455525, 455517, 455507, H04B 100, H04B 700
Patent
active
058227016
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a high-speed radio communication system suitable for mobile communication.
BACKGROUND ART
Conventionally, as a radio communication system to transmit information from a radio base station to terminals, there is a radio paging system (so-called pocket-bell service system) shown in FIG. 1. A detailed configuration of the radio paging system shown in FIG. 1 has been set forth in, for instance, a literature, Masaaki Sinji, "Mobile Communication", Maruzen Co., Ltd, 1989.
First, a person who puts through a call (caller) issues a call request via the fixed telephone, etc. Once the call request has been issued, a call signal is transmitted from a calling base station 103 to a radio call receiving station 105 to effect a calling.
This radio paging system is a one-way transmission system and therefore only down transmission from the radio base station to the receiving terminal is carried out. Therefore, since transmitting function is not needed for the reception terminal, miniaturization/low consumption power of the reception terminal can be achieved. As mentioned above, the radio paging system is a one-way transmission system. However, the radio paging system can be used as an equivalent two-way communication system if it is combined with the fixed telephone which is connected to the cable public telephone (switched) network, for example, and therefore such radio paging system has been widely used.
Further, in order to improve receiving quality in the radio paging system, a multistation simultaneous transmission has been effected by transmitting simultaneously signals from a plurality of radio base stations to a certain terminal to attain a diversity effect.
In such multistation simultaneous transmission, offset transmission is often employed wherein carrier frequency, modulation waveform, or frequency deviation is offset intentionally in the radio base station. In case this offset transmission is employed, fading frequency of the signal received by the receiving terminal is accelerated rather than that obtained when the offset transmission is not employed. As a result, probability that a receiving level is less than that required for achieving normal transmission quality can be lessened to thus improve transmission characteristics. This fact has been disclosed, for example, in the above literature "Mobile Communication".
However, in this offset transmission, there has been such a drawback that expansion of required signal bandwidth is caused due to offset to reduce frequency utilization efficiency.
Therefore, as the multistation simultaneous transmission without expansion of the signal bandwidth, such a system has been examined that delayed symbol timings are transmitted intentionally between a plurality of radio base stations on the transmitter side and then these delayed waves are synthesized by an equalizer in the receiving terminal on the receiver side. In the case of this system, a so-called path diversity effect can be obtained because propagation paths from respective radio base stations to terminals can be considered to be independent. This fact has been set forth in patent application Ser. No.62-120130, entitled "Transmission Path Diversity Transmission System", and patent application Ser. No.2-148935, entitled "Diversity Receiver", and also disclosed in Per-Erik Ostling, "Performance of MMSE Linear Equalizer and Decision Feedback Equalizer in Single-Frequency Simulcast Environment", 43rd IEEE Vehicular Technology Conference, 1993, pp.629-632.
However, foregoing literatures merely disclose transmission systems, but no concrete transmission system including particular procedures to access radio channels, etc. have been proposed.
In addition, since transmission rate of the current radio paging system is 1.2 Kbit/sec at maximum, it is not feasible to transmit a great deal of information at high speed. Further, a transmission bandwidth must be expanded at the time of high-speed transmission of information. Since reception sensitivity is degraded owing to su
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Performance of MMSE Linear Equalizer and Decision Feedback Equalizer in Single Frequency Simulcast Environment, 43rd IEEE Vehicular Technology Conference, Jan. 1993, pp., 629-632.
Multitransmitter Digital Signal Transmission by Using Offset Frequency Strategy in Land-Mobile Telephone, IEEE Transactions on Vehicular Technology, vol. VT-27, No. 4, Nov. 1978, pp. 231-238.
Hirade Kenkichi
Suzuki Hiroshi
Tomisato Shigeru
Crosland Donnie L.
NTT Mobile Communications Network Inc.
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