System and method for wireless communication using a management server and access points

• US 20030236103A1
• Filed: 06/02/2003
• Published: 12/25/2003
• Est. Priority Date: 06/21/2002
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Yano, Takashi, Uta, Takaki, Ishifuji, Tomoaki, Tamaki, Tsuyoshi
• Granted Patent: US 7,319,684 B2
• Time in Patent Office: Days
• US Class Current: 455/552.1
• CPC Class Codes: H04L 41/00 Arrangements for maintenance, administration or management of data switching networks, e.g. of packet switching networks
• CPC Class Codes: H04W 16/28 using beam steering
• CPC Class Codes: H04W 28/14 using intermediate storage
• CPC Class Codes: H04W 52/243 taking into account interferences
• CPC Class Codes: H04W 72/542 using measured or perceived quality
• CPC Class Codes: H04W 74/0816 with collision avoidance

Abstract

A system and method are provided for wireless communication. In one example, a wireless communication system that enhances total system throughput is provided. The system performs parallel data transmission from a plurality of access points to a plurality of user terminals. On terminals with power control function, their transmit power can be set to minimize interference. The wireless communication system comprises a management server which performs centralized management of time of access-point-to-terminal packet transmission, access points, and user terminals that perform data transmission, according to transmission time control information from the management server. Transmit queues for measuring downlink traffic and receive queues for measuring uplink traffic are provided on the access points or the management server. The system determines uplink and downlink periods from the transmit and receive queue lengths. The system also controls the access points and user terminals to transmit for the determined periods. Consequently, packet collision due to transmission from a terminal that interferes with neighboring terminals is eliminated. Thus, system throughput is enhanced.

Claims

1. A communication system comprising:

one or more user terminals;

one or more access points configured to connect the one or more user terminals to a wired network; and

a management server, wherein the management server is configured to determine time of data packet transmission on the uplink as an uplink period and time of data packet transmission on the downlink as a downlink period, and wherein the management server is further configured to control time of transmission between the one or more access points and the one or more user terminals using control information.

2. The communication system of claim 1, at least one of the one or more access points comprises a transmit queue configured to measure downlink traffic from the one or more access points to the one or more user terminals.

3. The communication system of claim 1, wherein each of the one or more access points comprises one of:

a directional antenna configured to direct beams toward the one or more user terminals, and

a transmit power control function, wherein an asymmetric transmit/receive power distribution exists between a downlink from the one or more access points to the one or more user terminals and an uplink from the one or more user terminals to the one or more access points.

4. The communication system of claim 1, wherein each of the one or more access points comprises one of:

a directional antenna configured to transmit and receive wireless signals;

a wireless interface configured to perform wireless signal processing;

a wired interface configured to perform wired signal processing;

a transmit queue configured to store data packets from the wired interface to the wireless interface;

a measurement device configured to measure variable transmit queue lengths;

a control signal processing device configured to create control signals for notifying the management server of measurement results from the measurement device of transmit queue length and further configured to receive control signals about time of data packet transmission/reception consisting of the downlink period and the uplink period from the management server;

a transmit timing control device configured to control timing of writing from the transmit queue to the wireless interface;

a timer configured to provide time information for managing transmit and receive timing;

a synchronous pilot signal generator configured to generate synchronous pilot signals for synchronizing another access point with time information from the timer;

a transmission device configured to transmit the synchronous pilot signals through either the wireless interface or the wired interface; and

a synchronous pilot signal detector configured to detect synchronous pilot signals received through the wireless interface or the wired interface and further configured to rectify timer information from the timer.

5. The communication system of claim 1, wherein the one or more user terminals comprises:

a non-directional antenna configured to transmit and receive wireless signals;

a wireless interface configured to perform wireless signal processing;

an external interface configured to perform signal processing for interfacing with an external device;

a receive queue configured to store data packets received from the wireless interface to the external interface;

a transmit queue configured to store data packets transmitted from the external interface to the wireless interface;

a control signal processing device configured to receive control signals about time of data packet transmission from the one or more access points;

a transmit and receive timing control device configured to control timing of writing from the transmit queue to the wireless interface and further configured to control timing of writing from the receive queue to the external interface, based on information from the control signal processing part;

a timer configured to provide time information for managing transmit and receive timing; and

a synchronous pilot signal detector configured to get synchronous pilot signals for synchronizing the one or more access points with time information from the timer through the wireless interface and further configured to rectify time information from the timer.

6. The communication system of claim 2, wherein at least one of the one or more access points further comprises:

a wired interface configured to perform wired signal processing;

a database configured to register the measurements of transmit queue lengths obtained from the one or more access points;

a calculation device configured to calculate a control frame length, the control frame being a period in which time of data packet transmission between an access point and a user terminal is controlled, and further configured to calculate a ratio of uplink traffic, based on the one or more access point transmit and receive queue length data;

a control signal processing device configured to generate control signals from the management server to the one or more access points and further configured to interpret received control signals; and

a synchronous pilot signal generator configured to generate pilot signals for synchronizing the one or more access points.

7. The communication system of claim 1, wherein the management server comprises:

a wired interface configured to perform wired signal processing;

transmit queues configured to store data packets from the management server to the one or more access points;

receive queues configured to store data packets from the one or more access points via the management server to a wired network;

a measurement device configured to measure variable transmit and receive queue lengths;

a database configured to register measured transmit and receive queue lengths;

a calculation device configured to calculate control frame length in which time of data packet transmission between an access point and a user terminal is controlled and further configured to calculate a ratio of uplink period, based on the transmit and receive queue length data;

a control signal processing device configured to generate control signals from the management server to the one or more access points and further configured to interpret control signals;

a synchronous pilot signal generator configured to generate pilot signals for synchronizing the one or more access points; and

a switch configured to deliver data packets from the receive queues., control signals from the control signal processing part, and synchronous pilot signals from the synchronous pilot signal generator to the appropriate transmit queues.

8. The communication system of claim 4, wherein in order that a data packet transmitted from a first access point and received by a first user terminal does not collide with a reply packet transmitted from a second user terminal to a data packet transmitted from a second neighboring access point, reply packets are synchronized when being transmitted from the first and second user terminals, and wherein in order that the directional antennas of the first and second access points receive only reply packets from correspondent user terminals, respectively, transmission of data packets is scheduled so that both transmissions terminate at a same timing at the first and second access points.

9. The communication system of claim 4, wherein in order that a data packet transmitted from a first access-point and received by a first user terminal does not collide with a reply packet transmitted from a second user terminal to a data packet transmitted from a second neighboring access point, MAC wrappers are installed in each access point and each user terminal and the access point transmits a broadcast packet into which its MAC wrapper maps a header including destination information and data so that reply packet transmission from a user terminal does not take place during a downlink period, and on the user terminal, a MAC wrapper detaches the header from the received broadcast packet and a reply packet is transmitted from the user terminal to the access point during an uplink period.

10. A method of controlling access of a communication system including one or more user terminals and one or more access points, wherein the one or more access points are configured to enable transmission to a target user terminal without interference with other access points or user terminals, and wherein the user terminals are configured to enable data transmission without interference with other access points or user terminals, the method comprising:

assigning a downlink period of transmission from an access point to a user terminal and an uplink period of transmission from the user terminal to the access point;

allowing access points to perform concurrent transmission to correspondent user terminals and to halt user terminals from transmitting data; and

during the uplink period, allowing one user terminal to perform data transmission at a time.

11. The method of claim 10, wherein the access points perform transmission to target correspondent user terminals using at least one of a directional antenna and an output control circuit.

12. The method of claim 11, wherein the communication system includes a management server configured to manage the access points, and wherein when the access points perform transmission to the user terminals, the method further comprises exerting control to halt the transmission of a user terminal falling within a predetermined range of interference with a destination user terminal.

13. The method of claim 11, further comprising:

exerting control of the user terminals via the access points; and

under command of a management server, sending transmission control information to a user terminal that should be banned from doing transmission so that the transmission of the user terminal is banned for a suitable time period.

14. The method of claim 13, further comprising:

allowing the one or more access points to transmit concurrently to correspondent user terminals;

banning user terminals from transmitting reply packets and data during the downlink period; and

transmitting reply packets during the uplink period.

15. The method of claim 13, further comprising:

allowing the one or more access points to transmit concurrently to correspondent user terminals;

banning the user terminals from transmitting data;

allowing the user terminals to transmit reply packets during the downlink period; and

synchronizing reply packet transmissions from the user terminals.

16. The method of claim 13, further comprising:

storing the data packets to transmit in transmit queues of the one or more access points;

storing the received data packets in receive queues of the one or more access points;

reporting the states of the transmit and receive queues to the management server;

calculating a downlink period from the transmit queue state;

calculating an uplink period from the receive queue state;

calculating a control frame length;

calculating a ratio of the uplink period in the control frame length;

creating control signals based on results of the downlink period, the uplink period, the control frame length, and the ratio of the uplink period; and

sending the control signals to the one or more access points.

17. The method of claim 16, wherein the states of the transmit queues and the receive queues are the lengths of the queues.

18. A computer-readable medium carrying one or more sequences of one or more instructions for controlling a distributed storage system for controlling access of a communication system including one or more user terminals and one or more access points, the one or more sequences of one or more instructions including instructions which, when executed by one or more processors, cause the one or more processors to perform the steps of:

assigning a downlink period of transmission from an access point to a user terminal and an uplink period of transmission from the user terminal to the access point;

allowing access points to perform concurrent transmission to correspondent user terminals and to halt other user terminals from transmitting data; and

during the uplink period, allowing one user terminal to perform transmission at a time.

19. The computer-readable medium of claim 18, wherein the access points perform transmission to target correspondent user terminals using at least one of a directional antenna and an output control circuit.

20. The computer-readable medium of claim 19, wherein the communication system includes a management server configured to manage the access points, and wherein when the access points perform transmission to the user terminals, the instructions further cause the one or more processors to perform the step of exerting control to halt the transmission of a user terminal falling within a predetermined range of interference with a destination user terminal.