Multiplex communications – Communication techniques for information carried in plural... – Adaptive
Reexamination Certificate
2000-04-10
2004-02-17
Pham, Chi (Department: 2667)
Multiplex communications
Communication techniques for information carried in plural...
Adaptive
Reexamination Certificate
active
06693915
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method in a data transmission system according to the preamble of the appended claim
1
. Furthermore, the invention relates to a wireless data transmission system according to the preamble of the appended claim
11
.
2. Brief Description of Related Developments
The considerable increase in the use of information services especially as a result of the increase in Internet services and so-called World Wide Web (WWW) services has generated a need to develop faster data transmission services to transmit information between the information service provider and the terminal using the information service. Furthermore, most information services contain so-called multimedia information, such as images, video image and sound. The transmission of such multimedia information requires a high data transmission rate to implement the highest possible real-time degree in the data transmission.
Data transmission systems intended for office use, i.e. so-called local area networks (LAN) are primarily implemented as landline systems. Thus, the communication between the terminals and the server is implemented either electrically via a cable or optically via an optical fibre. The advantage of such a fixed system is that it is possible to achieve relatively high data transmission rates. The disadvantage of such a fixed data transmission network is that it is difficult to make changes and the terminals have to be placed relatively close to the coupling points intented for them, wherein the mobility of the terminal is affected. The implementation of such a fixed local area network in an existing building is not always successful, or it is expensive to install the cables afterwards. On the other hand, especially in older buildings, the existing data transmission cables are not necessarily suitable for fast data transmission.
There are several wireless data transmission systems under development to implement local area networks. Numerous landline data transmission systems are based on the use of radio signals in the data transmission. One such data transmission system for a local area network that is being developed and is based on radio data transmission is a so-called HIPERLAN (HIgh PErformance Radio Local Area Network). The term broadband radio access network (BRAN) is also used for such a radio network.
In the version 2 of the HIPERLAN data transmission system that is under development, the aim is to reach a data transmission rate in the order of 25 Mbit/s when the maximum connection distance is some tens of metres. Such a system is suitable to be used within the same building for example as an internal local area network for a single office. There is also a so-called HIPERACCESS data transmission system under development, the aim of which is to reach the same data transmission rate as in said HIPERLAN/2 data transmission system, but a connection distance of a few hundreds of meters, wherein the HIPERACCESS system is suitable to be used as a regional local area network for example in schools and larger building complexes.
The appended
FIG. 1
b
shows in a reduced manner the frame structure applied in the data link layer DLC of the HIPERLAN/2 system used as an example. The data frame FR is composed of control fields C, such as RACH (Random Access Channel), BCCH (Broadcast Control CHannel) and FCCH (Frequency Correction CHannel), and a data field D which comprises a fixed amount of time slots TS
1
, TS
2
, . . . , TSn, in which the actual useful information can be transmitted.
In the HIPERLAN/2 system, data transmission is based on time division multiple access TDMA, wherein there may be several simultaneous connections on the same channel, but each connection is allocated a time slot of its own in said frame, in which time slot information is transmitted. Because the data transmission quantity is not constant in every simultaneous connection, but varies temporally, a so-called adapting TDMA method is used in which the number of time slots allocated for each connection can vary from zero to maximum depending on the loading situation at the time and on the data transmission capacity allocated for the connection.
For the time division multiple access to work, the terminals coupled to the same node have to be synchronized with each other and with the transmission from the node. This can be achieved for example in such a way that the receiver of the wireless terminal receives signals on a channel. If a signal is not detected on the channel, the receiver changes over to receive on another channel, until all the channels have been examined or a channel is found on which a signal transmitted by an access point is detected. By receiving and demodulating this signal, it is possible to determine the moment of transmission of the control channel BCCH of the access point in question and to synchronize the terminal on the basis thereof. In some cases, the terminal can detect the signal of more than one access point, wherein the terminal advantageously selects the access point which has the strongest signal in the receiver, and performs the synchronization with this access point.
When the terminal is synchronized with the access point, the terminal can initiate a connection set-up to couple to this access point. This can be conducted advantageously in such a way that the terminal transmits on the RACH control channel a connection set-up request to the access point. In practice, this means that the terminal transmits in the time slot allocated to the RACH control channel and at the same time the access point listens to the communication on the channel i.e. receives signals on the channel frequency it is using. When the access point detects that a terminal is transmitting a connection set-up request message, it performs the procedures necessary for the connection set-up, such as resource allocation for the connection, if it is possible. In the resource allocation, the quality of service requested for the connection is taken into account, which affects e.g. the number of time slots to be allocated for the connection. The access point informs the terminal whether the connection set-up is possible or not. If the connection set-up is successful, the access point transmits in the BCCH control field e.g. data on the transmission time slots, reception time slots, connection identifier, etc. which are allocated for the connection. The number of transmission and reception time slots is not necessarily the same, because in several cases the quantity of information to be transmitted is not the same in both directions. For example when using an Internet browser, the quantity of information transmitted from the terminal is considerably smaller than the amount of information received in the terminal. Thus, with respect to the terminal, the required number of transmission time slots is smaller than that of reception time slots.
Furthermore, the number of time slots allocated for the connection can advantageously vary in different frames according to the need to transmit data. The access point controller is provided with a so-called scheduler, one function of which is the aforementioned allocation of time slots for different connections. The scheduler is implemented advantageously as an application program in the access point controller.
Since duplex data transmission is necessary in local area networks, duplex data transmission is also necessary on the radio channel. In a time division system this can be implemented either in such a way that some of the time slots of the frame are allocated for transmission from the wireless terminal to the access point (uplink) and some of them are allocated for the transmission from the access point to the wireless terminal (downlink), or in such a way that a separate frequency band is allocated for each data transmission direction. The HIPERLAN/2 system suggests the use of the former of the aforementioned methods, wherein the access point and the wireless terminals coupled to it do not transmit simultaneou
Lappeteläinen Antti
Smolander Visa Tapio
Väisänen Ari
Ly Anh-Vu H
Nokia Corporation
Perman & Green LLP
Pham Chi
LandOfFree
Efficient bandwidth allocation for high speed wireless data... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Efficient bandwidth allocation for high speed wireless data..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Efficient bandwidth allocation for high speed wireless data... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3304638