Efficient bandwidth allocation for high speed wireless data transmission system

• US 6,693,915 B1
• Filed: 04/10/2000
• Issued: 02/17/2004
• Est. Priority Date: 04/13/1999
• Status: Expired due to Fees

• Current Assignee: Nokia Corporation
• Original Assignee: Nokia Corporation
• Inventors: Smolander, Visa Tapio, Lappeteläinen, Antti, Väisänen, Ari
• Primary Examiner(s): Pham, Chi
• Assistant Examiner(s): LY, ANH VU H
• Application Number:
  US09/546,703
• Time in Patent Office: 1,408 Days
• Field of Search: 370/278, 370/280, 370/282, 370/294, 370/314, 370/321, 370/326, 370/329, 370/330, 370/331, 370/332, 370/336, 370/337, 370/338, 370/345, 370/347, 370/348, 370/437, 370/442, 370/443, 370/444, 370/447, 370/458, 370/468, 370/477
• US Class Current: 370/468
• CPC Class Codes: H04W 72/535 based on resource usage policies
• CPC Class Codes: H04W 72/541 using the level of interference

Abstract

The invention relates to a method in a wireless data transmission system (1) which comprises wireless terminals (MT1-MT4), at least a first access point (AP1) and a first access point controller (AC1), a second access point (AP2) and a second access point controller (AC2). In the data transmission, data frames are used. In the invention, two allocation strategies are defined of which two are selected at a time. From the data frames, a first starting point (TS11, TS21) and a second starting point (TS1n, TS2n) are determined. In order to select a strategy, it is examined whether there is other traffic on the channel. If other traffic can be detected, it is examined which allocation strategy is selected, and an allocation strategy which is different from that of the examined connection is selected for the connection to be set up. However, if traffic is not detected, it is possible to select the allocation strategy freely. In the first allocation strategy, the allocation of the time slots of the data field (D1, D2) is started from the first starting point (TS11, TS21) of the data field, and in the second allocation strategy, the allocation of the time slots of the data field is started from the second starting point (TS1n, TS2n) of the data field.

Claims

1. A method in a wireless data transmission system (1) which comprises wireless terminals (MT1-MT4), at least a first access point (AP1) and a first access point controller (AC1), and a second access point (AP2) and a second access point controller (AC2), in which method

first data frames (FR1) and second data frames (FR2) are established,

the controller (AC1) of the first access point controls the transmission and reception of the first data frames (FR1) between the first access point (AP1) and the wireless terminals (MT1, MT2) communicating with the first access point, wherein said first data frames (FR1) are used in the data transmission between the first access point (AP1) and the wireless terminals (MT1, MT2) communicating with the first access point,

the controller (AC2) of the second access point controls the transmission and reception of the second data frames (FR2) between the second access point (AP2) and the wireless terminals (MT3, MT4) communicating with the second access point, wherein said second data frames (FR2) are used in the data transmission between the second access point (AP2) and the wireless terminals (MT3, MT4) communicating with the second access point,

the first (FR1) and the second data frames (FR2) comprise at least one control field (C1, C2) and data field (D1, D2),

from said data field (D1, D2) time slots (TS11-TS1n, TS21-TS2n) are allocated for the communication of data transmission connections, and

in which wireless data transmission system (1) one or more channel frequencies are used in the transmission and reception of the data frames (FR1, FR2), wherein each data transmission connection is allocated one of said channel frequencies,

characterized in that also in the method

a first starting point (TS11, TS21) and a second starting point (TS1n, TS2n) are determined from said data field (D1, D2),

a first allocation strategy is determined, in which the allocation of the time slots (TS11-TS1n, TS21-TS2n) of the data field (D1, D2) is started from said first starting point (TS11, TS21) of the data field, and a second allocation strategy is determined, in which the allocation of the time slots (TS11-TS1n, TS21-TS2n) of the data field (D1, D2) is started from said second starting point (TS11, TS21) of the data field, and information on the allocation strategy used in the data frame (FR1, FR2) is attached to the data frame (FR1, FR2), and

the transmission and reception of the first data frames (FR1) is synchronized with the transmission and reception of the second data frames (FR2), wherein at the first access point (AP1), the allocation strategy of the second data frames (FR2) is examined, and that allocation strategy which is not used in the second data frames (FR2) is selected for the first data frames (FR1).

2. The method according to claim 1, characterized in that the beginning of the data field (D1, D2) is selected as said first starting point (TS11, TS21) and the end of the data field (D1, D2) is selected as said second starting point (TS1n, TS2n).

3. The method according to claim 1, characterized in that to synchronize the first data frames (FR1):

said at least one control field (Cl) of the first data frame (FR1) is scheduled before said at least one control field (C2) of the second data frames (FR2), if the allocation strategy selected for the second data frames is the first allocation strategy, or

said at least one control field (C1) of the first data frame (FR1) is scheduled after said at least one control field (C2) of the second data frames (FR2), if the allocation strategy selected for the second data frames is the second allocation strategy.

4. The method according to claim 1, characterized in that

the wireless terminal (MT1, MT2) communicating with the first access point (AP1) also receives data frames (FR2) transmitted on the channels adjacent to the channel frequency used in the data transmission connection,

the timing difference between the control field (C2) of at least one data frame received on said adjacent channels and the control field (C1) of the data frame in a data transmission connection of said wireless terminal (MT1, MT2) is determined,

information on said timing difference is transmitted to said first access point (AP1), and

the information on said timing difference is stored in the controller (AC1) of said first access point.

5. The method according to claim 4, characterized in that in the wireless terminal (MT1, MT2) communicating with the first access point (AP1), the strength of the radio signals is also measured on channels adjacent to the channel frequency used in the data transmission connection, and information on the strength of the signals is transmitted to said first access point (AP1).

6. The method according to claim 4, characterized in that a guard time is determined, wherein the synchronization of the data frames (FR1, FR2) is conducted on the basis of said timing difference and said guard time.

7. The method according to claim 4, characterized in that in the first access point (AP1), the channel frequency of at least one data transmission connection is changed, wherein to select a new channel frequency on the basis of the measurement data stored in the controller (AC1) of the first access point:

it is determined on which channel frequencies data frames (FR2) of other access points (AP2) have not been detected, wherein one for such channel frequencies is selected as the new channel frequency of said data transmission connection, and the allocation strategy can be selected irrespective of the other access points (AP2), or

if data frames (FR2) of at least one other access point (AP2) have been detected on each channel frequency used in said wireless data transmission system (1), it is determined on which channel frequencies the data frames (FR2) of at least one other access point (AP2) have been detected, wherein one of such channel frequencies is selected in the controller (AC1) of the first access point as a new channel frequency for said data transmission connection, it is examined which allocation strategy is selected for the data frames (FR2) of said other access point (AP2), and that allocation strategy is selected which is not used in the data frames (FR2) of said other access point (AP2).

8. The method according to claim 1, characterized in that

the first access point (AP1) also receives the data frames (FR2) transmitted on the channels adjacent to the channel frequency used in the data transmission connection,

the timing difference between the control field (C2) of at least one data frame received on said adjacent channels and the control field (Cl) of the data frame in a data transmission connection of said access point (AP1) itself is determined,

the information on said timing difference is stored in the controller (AC1) of said first access point.

9. The method according to claim 8, characterized in that in the first access point (AP1), the strength of the radio signals is also measured on the channels adjacent to the channel frequency used in the data transmission connection, and information on the signal strengths is transmitted to the controller (AC1) of said first access point.

10. The method according to claim 1, characterized in that the following stages are also executed in the first access point (AP1):

a) measuring a first timing difference between the data frames (FR1, FR2) of said first access point (AP1) and of said second access point (AP2),

b) measuring a second timing difference between the data frames (FR1, FR2) of said first access point (AP1) and of said second access point (AP2),

c) measuring the time passed between said first measurement and said second measurement,

d) changing at intervals the synchronization on the basis of said first and second timing difference and the time passed between the measurements,

wherein stages b) and c) are executed less frequently than stage d).

11. A wireless communication system (1) comprising

wireless terminals (MT1-MT4),

means (AC1, AC2) for forming first data frames (FR1) and second data frames (FR2),

at least a first access point (AP1) and a first access point controller (AC1), and a second access point (AP2) and a second access point controller (AC2),

means (AC1) for controlling the transmission and reception of first data frames (FR1) between the first access point (AP1) and the wireless terminals (MT1, MT2) communicating with the first access point, wherein said first data frames (FR1) are arranged to be used in the data transmission between the first access point (AP1) and the wireless terminals (MT1, MT2) communicating with the first access point,

means (AC2) for controlling the transmission and reception of the second data frames (FR2) between the second access point (AP2) and the wireless terminals (MT3, MT4) communicating with the second access point, wherein said second data frames (FR2) are arranged to be used in the data transmission between the second access point (AP2) and the wireless terminals (MT3, MT4) communicating with the second access point,

means for transmitting said data frames (FR1, FR2) between the wireless terminals (MT1-MT4) and the access points (AP1, AP2) on one or more channel frequencies of the wireless communication system (1), and

at least one control field (C1, C2) and data field (D1, D2) arranged in the first (FR1) and second data frames (FR2), wherein the wireless data transmission system (1) comprises means (AC1, AC2) for allocating time slots (TS11-TS1n, TS21-TS2n) from said data field (D1, D2) for the data transmission of data transmission connections,

characterized in that in the wireless data transmission system (1)

a first starting point (TS11, TS1n) and a second starting point (TS21, TS2n) are determined from said data field (D1, D2) of the data frame, and a first allocation strategy is determined, wherein the allocation of the time slots (TS11-TS1n, TS21-TS2n) is arranged to be started from said first starting point (TS11, TS21) of the data field, and a second allocation strategy is determined, wherein the allocation of the time slots in the data field is arranged to be started from said second starting point (TS1n, TS2n) of the data field, and

that the wireless data transmission system (1) also comprises:

means for transmitting the allocation strategy used in the data frame (FR1, FR2) in the data frame,

synchronizing means for synchronizing the transmission and reception of the first data frames (FR1) with the transmission and reception of the second data frames (FR2),

means for examining the allocation strategy of the second data frames (FR2), and

means for selecting an allocation strategy for the first data frames (FR1) on the basis of the allocation strategy of the second data frames (FR2).

12. The wireless data transmission system (1) according to claim 11, characterized in that the said first starting point (TS11, TS21) determined is the beginning of the data field (D1, D2) and the said second starting point (TS1n, TS2n) determined is the end of the data field (D1, D2).

13. The wireless data transmission system (1) according to claim 11, characterized in that the synchronizing means comprise:

scheduling said at least one control field (C1) of the first data frame (FR1) before said at least one control field (C2) of the second data frames (FR2) if the allocation strategy selected for the second data frames is the first allocation strategy, or

scheduling said at least one control field (C1) of the first data frame (FR1) after said at least one control field (C2) of the second data frames (FR2) if the allocation strategy selected for the second data frames is the second allocation strategy.

14. The wireless data transmission system (1) according to claim 11, characterized in that

the wireless terminal (MT1, MT2) communicating with the first access point (AP1) comprises means for receiving the data frames (FR2) transmitted on the channels adjacent to the channel frequency used in the data transmission connection,

means for determining the timing difference between the control field (C2) of at least one data frame received on said adjacent channels and the control field (C1) of the data transmission connection of said wireless terminal (MT1, MT2) itself,

means for transmitting the information on said timing difference to said first access point (AP1) and

means for storing said timing difference to the controller (AC1) of said first access point.

15. The wireless data transmission system (1) according to claim 11, characterized in that the wireless terminal (MT1, MT2) comprises measuring means for measuring the strength of radio signals on channels adjacent to the channel frequency used in the data transmission connection, and means for transmitting the information on the signal strengths to said first access point (AP1).

16. The wireless data transmission system according to claim 11, characterized in that it is a wireless local area network.