CN1158788C - Packet transmission method - Google Patents

Abstract

A wireless system includes base station transceivers (102-104) to communicate with at least one mobile station (108), the base station transceivers communicate with a network controller (110). The base station controls a header for a packet frame to be communicated between the base station transceiver and the network controller wherein a portion of the header identifies the frame as one containing no data package. The data bits of the header field may contain a predetermined bit pattern for a frame including no data package. Information received by the base station from the mobile station may be dropped, and the header information replaced with the specified bit pattern, if a decoding metric passes a threshold. The information received by the base station from the mobile station may be dropped, and the header information replaced with the specified bit pattern, if a CRC for the frame received from the mobile station fails.

Description

packet transfer method

field of invention

This invention relates to packet transmission, and more particularly to packet transmission between cellular base transceiver stations and network switches.

background of the invention

In a wireless cellular data communication system such as a Code Division Multiple Access (CDMA) system, packets or frames delivered from a Base Transceiver Station (BTS) and a Radio Network Controller (RNC) include headers with control and quality information and include data useful load. These communications are often referred to as backhauls. In these systems, the payload may include data, control messages, or other information related to the operation of the mobile station or base transceiver station. The data payload portion of the packet or frame may contain padding bits when data is not present. The RNC ignores these padding bits.

Detour loads can limit overall system capacity. In many cases, detour loads are not an issue. However, as data requirements increase in existing systems, and capacity reaches its limits, detour loads may limit system capacity. Therefore, there is a need for a method that reduces load without negatively impacting communications.

Brief description of the drawings

Figure 1 is a block diagram illustrating a cellular communication system;

FIG. 2 illustrates frames or packets communicated between a base transceiver station and a network according to the communication system shown in FIG. 1. FIG.

Detailed description of the drawings

A wireless communication system includes a base transceiver station in communication with at least one mobile station, the base transceiver station in communication with a network controller. The base station controls headers of packet frames passed between the base transceiver station and the network controller, wherein a portion of the header identifies a frame when the frame does not contain data packets. The data bits of the header field may contain a predetermined bit pattern for frames that do not contain data packets. If the decoding metric passes a threshold, the base station may discard the information received from the mobile station and replace the header information with a specific bit pattern. If the CRC of the frame received from the mobile station fails, the base station may discard the information received from the mobile station and replace the header information with a specific bit pattern.

FIG. 1 discloses a cellular system 100 . The illustrated cellular system 100 is a code division multiple access system comprising a plurality of base transceiver stations (BTS) 102-104 communicating with mobile station MS 108 on respective wireless communication paths. Those skilled in the art will appreciate that typically there will be more than 3 base transceiver stations and more than 1 mobile station present in the system. The base transceiver stations 102-103 are connected to a network 110 of the mobile switching system. The infrastructure (network controller) responsible for controlling, regulating, and initializing base transceiver stations is often referred to as a central base station controller (CBSC), or a radio network controller (RNC), or a selection/distribution unit (SDU). Digital cellular systems of this type are well known. During normal operation it is used for detour communications between the BTS and the network controller for system control and outbound communications.

For packet, circuit or voice data, when the BTS demodulator is not decoding the signal from the MS, there is no need to transfer the packet payload from the BTS to the RNC. It is obvious that bits or unassigned bit patterns can be appended to the header of packet 200 (FIG. 2). Preferably, an existing bit field of the header passed between the base transceiver station and the network controller is used to indicate that the data payload is empty. Although any header may be used, the bits in the header will be used as the Signal Error Rate (SER), eg the "Signal to Thermal Noise Ratio" octet in packet 200 . This field is used to indicate signal quality when data payload (reverse link information) is present. If the payload is not present, this field may conveniently be used to transmit a predetermined bit pattern (or one bit of the octet may be a flag) indicating that the payload is not present.

In operation, when a signal is transmitted to the RNC 110, the BTSs 102-104 insert predetermined bits or patterns into selected fields. The RNC checks to see if a predetermined pattern or flag is found, indicating in the header the presence of "reverse link information", here called payload. If there is a payload, it is handled in the normal way. If no payload is present, the frame is still processed in the same way as long as the payload is stuffing bits.

Those skilled in the art know that the cyclic redundancy check (CRC), which resides in the data payload, will not be present if the data payload is removed from the packet or frame. Obviously the CRC can be provided to the header, or the CRC of the payload can be used. If a payload CRC with missing payload is used, the payload CRC will only be calculated on the header.

Thus, it can be seen that the bit pattern of the frame type bit field of the packet header can be chosen to indicate that no payload is attached. Optional use of new fields in packet headers.

The present invention can be advantageously used when none of the pointers assigned by the BTS to a given user is in a locked state to more efficiently use the reverse detour bandwidth by not discarding filter data for frame intervals. An example of transmission of padding data in existing systems is when none of the channel demodulators (pointer: finger) corresponding to a given mobile station (or terminal equipment) communication link is "locked", which may be in the soft Switch from a weak service path to a strong service path during handover. The normal operation of a Base Transceiver Station (BTS) of a Code Division Multiple Access (CDMA) cellular system requires that pointers be assigned to signal paths received at a serving base station in communication with a mobile station. After each search interval, there is a set of pointer management rules applied to active (active means pointers (demodulators) are currently assigned to offsets) pseudorandom noise (PN) offsets and potential PN offset candidates to determine pointer allocation. PN offset candidates are determined by the searcher when the energy of a given signal path exceeds a certain search threshold. The active PN offsets have pointers assigned to them and are demodulated by the following soft combining and decoding.

When the energy assigned to an active PN offset pointer falls below the "lock" threshold, that pointer is deallocated so that no demodulation occurs for that pointer, and that pointer is no longer used in diversity combining. The deallocated pointer can then be reallocated to a more promising PN candidate, if one exists. does not occur if the searcher does not detect any PN offset with enough energy to report to the pointer manager, and all existing active (locked) pointers abort lock because their respective energies drop below the lock threshold demodulation. At this point, the discarded data of the payload frame to the RNC is set to a predetermined pattern (eg, all zeros).

Therefore, there is no need to discard the payload portion for a given frame interval when the pointer is not locked due to no valid bit decoding. Elimination of unnecessary useful load reduces detour bandwidth requirements (detour bandwidth refers to the infrastructure at the base transceiver station and is responsible for controlling, adjusting, and initializing the base transceiver station, commonly referred to as CBSC, or RNC, or SDU between the required communication bandwidth). Therefore, soft handoff between carriers is provided to provide an indication of this situation, where the header is returned to the RNC alone without the data payload.

This concept can be extended to a case when a frame is deleted at the BTS (eg where a CRC check fails), even though some pointers are still locked. Since some deleted frames still have useful information, and the corresponding payload is needed at the RNC, it is possible to determine whether useful Soft decisions are made on decisions to load or drop frames. Examples of quality frame metrics can be used for decisions whether to transmit data including aggregate metrics or bit energy metrics (BER), such as estimated signal-to-interference ratio (SIR), signal-to-noise ratio (SNR), or Eb/Nt, among others.

Thus, it is known that a system has been disclosed for allocating a new bit or bit pattern using an unallocated existing field in the packet header to indicate the absence of the data payload portion of the packet. This can narrow the bandwidth of the average detour. The present invention is particularly useful when none of the subscriber's assigned pointers are locked at a given serving base transceiver station (BTS), but it can also be extended to delete at the discretion of the carrier/operator with Frames with high SER.

Claims (4)

1. the block transmission method in the wireless system, described wireless system comprise at least and the base station transceiver of a mobile communications that described base station transceiver is communicated by letter with network controller, and described method comprises the steps:

In base station transceiver, be controlled at the header of the packet frames of transmitting between base station transceiver and the network controller, wherein, when a frame did not comprise packet, the part of this header identified this frame; And

With constructed header this frame is transferred to network controller.

2. block transmission method as claimed in claim 1, wherein for the frame that does not comprise packet, the data bit of this header fields comprises a predetermined bit code type.

3. block transmission method as claimed in claim 1, if wherein decoding metrics is by thresholding, then the base station abandons the information that receives from travelling carriage, and header information is replaced by specific bit code type.

4. block transmission method as claimed in claim 1, if wherein for the CRC check failure from the frame that travelling carriage received, then the base station abandons the information that receives from travelling carriage, and header information is replaced by specific bit code type.

Images