Multiplex communications – Communication over free space – Having a plurality of contiguous regions served by...
Reexamination Certificate
1999-10-04
2004-02-24
Tran, Sinh (Department: 2681)
Multiplex communications
Communication over free space
Having a plurality of contiguous regions served by...
C370S342000, C370S441000
Reexamination Certificate
active
06697346
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method and to devices for transmitting and receiving data in a code division multiple access telecommunication system.
BACKGROUND OF THE INVENTION
A telecommunication system is a system, in which data are communicated between one or more base stations and one or more mobile stations. Thereby, the communication area is divided in cells, in which one base station communicates with one or more mobile stations. Multiple access systems are used to support the simultaneous access of a plurality of mobile stations to one base station within the limited resources of the transmission system. Several multiple access systems are known, e.g. frequency division multiple access (FDMA), time division multiple access (TDMA), or code division multiple access (CDMA). Additional to these basic types of multiple access systems, combinations of these different systems are possible and in practical use. The GSM-System for example uses a combination of FDMA and TDMA.
The present invention particularly relates to the transmission and reception of random access data in a code division multiple access system. Random access data are transmitted in the so-called random access slot (RACH) from a mobile station to build up a connection or to transmit data. The random access data from the mobile station contain a request, if the base station has sufficient resources available to build up the required connection or to transfer user data.
The random access slot comprises or consists of succeedingly or periodically provided random access time windows, in which several random access slots are available. The different random access slots are randomly chosen by a mobile station for the transmission of random access data. In a currently proposed wide band direct sequence CDMA (WCDMA) system, the random access time windows are based upon an initial preamble scrambling code, which differentiates between one cell and another cell. Thereby, these codes need to be planned to ensure that neighboring cells do not use the same code. Therefore, within the preamble part of each random access slot burst, is provided the preamble signature, which is one of 16 separate codes available for use within that cell. These 16 codes can be seen as separate slots. One of these codes is chosen randomly by the mobile station for the transmission of random access data. Beforehand, the base station broadcasts, which codes are available in each cell over the broadcast control channel (BCCH). In addition, within one time frame (10 ms) are provided 8 time offsets, each of 1,25 ms, allowing a further 8 variations. In other words, in each time frame a random access time window is provided, which comprises a plurality of random access slots for transmitting random access data from one or more mobile stations to the base station. The random access time window thereby extends over the time frame of 10 ms, so that 128 different random access slots (16 separate preamble codes and 8 time offsets) are provided within one random access time window.
A collision, i.e. a situation, where messages from two or more mobile stations collide and are lost, only occurs, when both the preamble code and the time offset are chosen in the same random access time window. In practice, it is expected that only about 30% of the theoretical maximum of 128 accesses per 10 ms will be possible.
In a situation, where a number of packet data users are operating in a bursty traffic situation, this maximum could be quickly reached. In such a situation the access to the network will either become slower or not be possible at all. This is due to congestion caused by the build up of first time requests and the retransmissions made necessary by previous collisions. Since the access to the random access slots is only contention based as shown in
FIG. 1
, a guaranteed upper limit on the amount of time needed to access the system even after an initial burst is not ensured. For packet data applications, which demand a constant periodic delivery of data, ready access is critical.
WO 98/24250 discloses a TDMA system, which allocates a fixed random access slot constantly to a particular mobile station.
The object of the present invention is thus to provide a method and devices for transmitting and receiving data in a code division multiple access telecommunication system, in which a random access time window comprising a plurality of random access slots for transmitting random access data is provided, whereby the random access time window is partioned on the basis of a partition point in the first section comprising contention based random access slots and a second section comprising reservation based random access slots, and in which an optimal setting of the partition point is ensured, so that the random access time window resources are fully utilized. The importance of an effective random access slot utilization arises particularly from increased load from packet data capacity requests and the transfer of small amounts of user data within random access slot burst.
This object is achieved by a method for transmitting and receiving data in a code division multiple access telecommunication system, comprising the steps of providing a random access time window comprising a plurality of random access slots for transmitting random access data from at least one communication device to a second communication device, determining a partition point defining a number of contention based random access slots and a number of reservation based random access slots in the random access time window on the basis of statistical information generated in at least one first communication device, and partitioning the random access time window in a first and a second section on the basis of said partition point, whereby the first section contains contention based random access slots and the second section contains reservation based random access slots. The first communication devices can thereby be mobile stations and the second communication device can thereby be a base station of the telecommunication system. Reservation based random access slots are slots which cannot be accessed on a contention basis, but only if they had been reserved before.
The above object is further achieved by a device for transmitting and receiving data in a code division multiple access telecommunication system, in which a random access time window comprising a plurality of random access slots for transmitting random access data is provided, the random access time window being partitioned in a first and a second section, whereby the first section contains contention based random access slots and the second section contains reservation based random access slots, with means for randomly choosing a random access slot from said first section, means for transmitting random access data in said chosen random access slot, and means for generating statistical information on contention based random access attempts. This device for transmitting and receiving data is e.g. a mobile station of the telecommunication system.
The above object is further achieved by a device for transmitting and receiving data in a code division multiple access telecommunication system, in which a random access time window comprising a plurality of random access slots for transmitting random access data is provided, with means for determining a partition point defining a number of contention based random access slots and a number of reservation based random access slots and a random access time window on the basis of received statistical information, means for partitioning the random access time window in a first and a second section on the basis of said partition point, whereby the first section contains contention based random access slots and the second section contains reservation based random access slots, and means for broadcasting information on the partition point of said random access time window. This device for transmitting and receiving data can for example be a base station of the telecommunicati
Halton John
James Paul
Frommer William S.
Frommer & Lawrence & Haug LLP
Polito Bruno
Ramos-Feliciano Eliseo
Sony International (Europe) GmbH
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