Variable modulation communication method and system

• US 5,577,087 A
• Filed: 10/27/1992
• Issued: 11/19/1996
• Est. Priority Date: 10/31/1991
• Status: Expired due to Term

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Furuya, Yukitsuna
• Primary Examiner(s): Tse, Young T.
• Assistant Examiner(s): WEBSTER, BRYAN E
• Application Number:
  US07/967,278
• Time in Patent Office: 1,484 Days
• Field of Search: 375/39, 375/17, 375/67, 375/83, 375/102, 375/84, 375/261, 375/260, 375/264, 375/267, 375/279, 375/283, 375/286, 375/298, 375/317, 375/299, 375/329, 375/332, 375/334, 375/333 , 375/324, 375/340, 375/346, 375/347, 375/349, 375/40, 370/85.7, 370/17, 370/79, 370/95, 329/304, 329/306, 455/277.2, 455/226.1-226.4, 371/20.1, 371/32, 371/33, 371/34, 371/56, 371/55, 332/103, 332/104
• US Class Current: 375/377
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0007 by modifying the frame length
• CPC Class Codes: H04L 1/0022 in which mode-switching is influenced by the user
• CPC Class Codes: H04L 1/0025 Transmission of mode-switching indication
• CPC Class Codes: H04L 27/0008 arrangements for allowing a transmitter or receiver to use more than one type of modulation negotiating modulation type for two-way transmission paths H04L5/1453

Abstract

In a variable modulation communication method, the transmission quality of a transmission path is monitored. If the transmission quality is good, communication is performed while the transmission time is shortened by using a multilevel modulation scheme. If the transmission quality is bad, communication is performed while the transmission time is prolonged by using a modulation scheme having a smaller number of levels than the multilevel modulation scheme. A variable modulation communication apparatus is also disclosed.

Claims

1. A variable modulation communication method comprising the steps of:

monitoring the transmission quality of a transmission path; and

selecting a shortened transmission time using a multilevel modulation scheme if the transmission quality of the transmission path exceeds a preset threshold, and selecting a lengthened transmission time using a modulation scheme having a smaller number of levels if the transmission quality of the transmission path is below said preset threshold.

2. A method according to claim 1, wherein a QAM modulation scheme is used as the first multilevel modulation scheme, and a PSK modulation scheme is used as the second multilevel modulation scheme having the smaller number of levels.

3. A method according to claim 1, wherein a plurality of terminals are arranged for performing time-division multiplexing communication with a base station upon time slot allocation, and fewer time slots are allocated to a terminal using the first multilevel modulation scheme than to a terminal using the second multilevel modulation scheme having the smaller number of levels.

4. A method according to claim 3, wherein said terminal using the first multilevel modulation scheme is allocated one time slot within a frame, and said terminal using the second multilevel modulation scheme having the smaller number of levels is allocated a plurality of time slots within said frame.

5. A variable modulation communication apparatus comprising:

first modulation means for performing multilevel modulation of digital data;

second modulation means for performing modulation of digital data with fewer levels than said first modulation means;

monitor means for monitoring transmission quality of a transmission path in order to determine a modulation scheme, said modulation scheme being carried out by one of said first and said second modulation means;

TDMA control means for performing time slot allocation differently depending on whether said first or second modulation means is used to carry out said modulation scheme, and performing time-division multiplexing communication control by using predetermined time slots which are allocated more in number when said second modulation means is used to carry out said modulation scheme than when said first modulation means is used to carry out said modulation scheme, thereby obtaining an identical information communication rate regardless of whether said first or said second modulation means is used;

switch means for selectively switching time-division output data from said TDMA control means to output the data to said first and said second modulation means; and

control means for controlling said switch means and said TDMA control means on the basis of said modulation scheme determined by said transmission quality monitored by said monitor means to selectively enable said first or said second modulation means.

7. An apparatus according to claim 5, wherein said monitor means, which is arranged in a terminal, sends a request for the modulation scheme to a base station, said control means controls said switch means and said TDMA control means on the basis of the modulation scheme which is designated by said base station in accordance with a power level of a received signal from said terminal.

8. An apparatus according to claim 7, wherein a QAM modulation scheme is used by said first modulation means for performing said multilevel modulation of digital data and a PSK modulation scheme is used by said second modulation means for performing said modulation of digital data with fewer levels.

9. An apparatus according to claim 7, wherein a plurality of terminals are arranged for performing time-division multiplexing communication with said base station upon time slot allocation, and fewer time slots are allocated to one of said plurality of terminals having said modulation scheme carried out by said first modulation means than to another of said plurality of terminals having said modulation scheme carried out by said second modulation means.

10. An apparatus according to claim 7, wherein one of the plurality of terminals having said modulation scheme carried out by said first modulation means is allocated one time slot within a frame, and another of said plurality of terminals having said modulation scheme carried out by said second modulation means is allocated a plurality of time slots within said frame.

6. A variable modulation communication method comprising the steps of:

transmitting a control signal from a base station to a terminal by using a first multilevel modulation scheme;

receiving said control signal by said terminal and monitoring a transmission quality of said control signal on a transmission path on a basis of a power of said control signal received;

determining, based on the monitored transmission quality, whether to use said first multilevel modulation scheme or a second multilevel modulation scheme having a larger number of levels than said first multilevel modulation scheme;

transmitting a connection request signal from said terminal to said base station on a basis of a communication request made by a user at said terminal, said connection request signal including information on the determined one of said first and second multilevel modulation schemes;

receiving said connection request signal at said base station and checking a reception quality of said connection request signal at said base station;

determining, at said base station, whether said determined one of said first and second multilevel modulation schemes can be performed for communication between said base station and said terminal based on said reception quality of said connection request signal;

at a same time as the determining step is performed at said base station, searching at said base station for a free communication channel and a modulation scheme;

determining a communication channel and modulation scheme for the communication between said base station and said terminal based on the searching step;

sending, from said base station to said terminal, a communication signal which includes information related to said communication channel and modulation scheme for communication between said base station and said terminal;

receiving said communication signal at said terminal and sending an acknowledgement signal from said terminal to said base station; and

at a same time as said terminal sends said acknowledgement signal, shifting a communication channel for transmission and reception of information at said terminal to said communication channel included in said communication signal, selecting a modulation scheme for the transmission and reception of information at said terminal in accordance with said modulation scheme included in said communication signal, and setting up time slots for the transmission and reception of information at said terminal in accordance with said modulation scheme included in said communication signal.