|Publication number||US20060268717 A1|
|Application number||US 11/496,590|
|Publication date||Nov 30, 2006|
|Filing date||Aug 1, 2006|
|Priority date||May 15, 2001|
|Also published as||US7099346|
|Publication number||11496590, 496590, US 2006/0268717 A1, US 2006/268717 A1, US 20060268717 A1, US 20060268717A1, US 2006268717 A1, US 2006268717A1, US-A1-20060268717, US-A1-2006268717, US2006/0268717A1, US2006/268717A1, US20060268717 A1, US20060268717A1, US2006268717 A1, US2006268717A1|
|Original Assignee||Golden Bridge Technology, Inc.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Referenced by (22), Classifications (14)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This application claims the benefit of U.S. Provisional Application No. 60/290,642 entitled “CHANNEL CAPACITY OPTIMIZATION FOR PACKET SERVICES ” filed on May 15, 2001, the disclosure of which is entirely incorporated herein by reference.
The present subject matter relates to spread-spectrum communications, and more particularly to a code-division-multiple-access (CDMA) cellular, packet-switched communication system, which comprises a radio network controller (RNC), a plurality of base stations and a plurality of remote stations. The subject matter relates more particularly to methods to facilitate transitions between different channels and performance of the channels, in such a system.
Recent developments in wireless communications technologies have allowed expansion of service offerings from the original voice telephone service model to include a number of services supporting packet data communications. As customers become increasingly familiar with data services offered through landline networks, they are increasingly demanding comparable Quality of Service (QoS) data communications in the wireless domain, for example to maintain service while mobile subscribers roam freely or to provide remote service in locations where wireless loops are preferable to landline subscriber loops. A number of technologies support packet data communications in the wireless domain.
Under the currently proposed W-CDMA technical specification, there is only one type of dedicated transport channel, the Dedicated Channel (DCH), which can be either a downlink or an uplink transport channel. There are six types of common transport channels:
1. The Broadcast Channel (BCH)—downlink;
2. The Forward Access Channel (FACH)—downlink;
3. The Paging Channel (PCH)—downlink;
4. The Random Access Channel (RACH)—uplink;
5. The Common Packet Channel (CPCH)—uplink; and
6. The Downlink Shared Channel (DSCH)—shared downlink, associated with one or several downlink DCH.
With these transport channels, there are two states in the connected mode that can potentially be used to transfer packet data over the W-CDMA air interface: the Cell-FACH state and the Cell-DCH state.
In the Cell-FACH state, there are two sub-states: the RACH/FACH sub-state and the CPCH/FACH sub-state. A mobile station in the CPCH/FACH sub-state is prepared to send packets via the CPCH while tuned in to the FACH for downlink messages. In the Cell-FACH state, the Radio Network Controller (RNC) can allocate RACH or CPCH resources for uplink transmission. CPCH and RACH may be assigned by the RNC as default channels in the uplink without using uplink resources until they are needed for transmission of uplink data. RACH is able to transmit very small Packet Data Units (PDUs) effectively. RACH capacity is limited to 9 bytes at cell edge or to 75 bytes when the mobile station is close to the base station. Sequential RACH transmissions may be used to transport more PDUs than a single RACH may carry, however, the RACH access procedure must be executed for each RACH access and the subsequent delay is significant. The RNC sets a threshold measurement of traffic volume in the mobile station, essentially instructing the mobile station to send a measurement report to the RNC when, for example, the traffic volume in the mobile station uplink buffer exceeds the capacity of two RACH transmissions. That would be the load at which it would make sense to utilize a higher capacity channel to transmit the buffered uplink data. If the measurement report is triggered, the RNC may assign CPCH resources to empty the uplink buffer or can switch the mobile station to Cell-DCH state.
CPCH may be assigned instead of RACH, to provide higher capacity uplink transport. A single CPCH access may transport up to 576×16 bytes of data at the cell edge (64 frames at SF 16) or up to 36,864 bytes when the mobile station is near the base station (64 frames at Spreading Factor 4). When CPCH resources are assigned to a mobile station, the RNC sets a threshold measurement of traffic volume in the mobile station, essentially instructing the mobile station to send a measurement report to the RNC when traffic volume in the mobile station uplink buffer exceeds the capacity of five to ten CPCH transmissions. Consecutive RACH or CPCH accesses may be used until the uplink buffers are emptied.
In the Cell-DCH state, there are the DCH/DCH sub-state and the DCH/DCH+DSCH sub-state. That means the mobile station sends packet data via the DCH uplink and is tuned to receive data downlink via either the DCH or the DCH+DSCH. The DSCH is a code-sharing mechanism in the downlink direction and is more desirable when data traffic is bursty. The DCH is more suitable for streaming traffic and is not a resource efficient means of transmitting bursty uplink data. In the uplink, DCH is different in that dedicated resources in the uplink must be allocated by the RNC without complete knowledge about the amount of data to be transmitted in the uplink. For this reason an inactivity timer is used in DCH to determine if the uplink buffer at a mobile station is emptied. The RNC will measure the time period in the uplink during which there is no uplink data transmission. When this period exceeds the inactivity timer setting, the RNC will reconfigure the mobile station to Cell-FACH. In the downlink, the Radio Network Controller (RNC) can allocate either DCH or DCH+DSCH resources for packet data transmission. Similarly, the RNC does not have complete knowledge of future packet arrivals and uses instead inactivity timers to measure the time period in the downlink during which there is no data transmission. When this period exceeds the inactivity timer setting, the RNC will reconfigure the mobile station to Cell-FACH. These inactivity timers in CELL-DCH lead to substantial overhead and inefficiencies when the data traffic is bursty, thus reducing capacity.
For certain types of packet data applications (e.g. interactive service), ideally, one would like to use a Cell-FACH (e.g. CPCH/FACH sub-state) for uplink traffic and switch to a Cell-DCH state (e.g. DCH/DCH+DSCH sub-state) for downlink traffic. The reason is that there are certain deficiencies with both states. In Cell-FACH state, FACH downlink does not have closed loop power control and has only limited capability to handle large packets, whereas in the Cell-DCH state, as in any circuit-switched packet channel, there is a lot of wastage of limited resources. However, a problem with the proposed frequent switching is that a mobile station while residing in the Cell-DCH state cannot be de-allocated immediately after transmission of packet data due to the inactivity timer.
Also, when a group of packets arrive from afar, as in the case of a backbone network, there will often be time-gaps between these packets. When the RNC assigns channel resources immediately after the arrival of the first packet and does not release such resources until the last packet of the train arrives, the channel hold-up time will increase, thus creating inefficiencies.
The inventions disclosed here deal with this type of deficiencies in the Cell-DCH state and the transition criteria or improvement between the Cell-FACH and Cell-DCH states on CDMA networks. The concepts and improvements described herein can also be generalized and applied to other channels as well as to other wireless digital packet communication networks.
The inventive concepts include a method for grouping a plurality of packets and sending these grouped packets in a shorter connecting time. This methodology introduces a quick release, for example, of the DCH resource associated with DCH or DCH+DSCH. By grouping the plurality of packets or reducing the release time of the DCH, the mobile station will more easily oscillate between the Cell-FACH and Cell-DCH states to support interactive type or the near-real time conversational applications of packet communications.
A general objective of the invention is to remove the inefficiencies associated with bursty data.
A further objective is to efficiently configure limited physical channel resources to various mobile stations. By reducing the connection time of a channel, the mobile station also reduces power consumption.
Another objective relates to provide a mechanism to release the DCH resources associated with the Cell-DCH state quickly.
A further objective is to enable mobile stations to oscillate between the Cell-FACH and Cell-DCH states.
A wireless packet communication network, such as a code-division-multiple-access (CDMA) telecommunication system employing spread-spectrum modulation, has a radio network controller (RNC) and a plurality of base stations, which serve a plurality of mobile stations. The term “mobile station” is used here to refer to any wireless remote user station, most examples of which are moveable, although some maybe used in fixed wireless applications. In a CDMA embodiment, each base station has a BS-spread-spectrum transmitter and a BS-spread-spectrum receiver. Each of the mobile stations has an MS-spread-spectrum transmitter and an MS-spread-spectrum receiver.
The RNC may be a physical network control node or a control application running on a network node that also implements other functions, for example on each of the base stations. In the preferred embodiment, the RNC monitors channel configuration, based on traffic measurement information of communications through the base stations for the mobile stations. Based on the traffic demand or a projection thereof, the RNC configures the physical channel resources within each cell.
The Radio Network Controller (RNC) waits to receive a packet for a mobile station (MS) from a core network. In accord with one inventive technique, while waiting for the first packet, the RNC sets its maximum packet accumulation timer, Timeracc, to a predetermined time and resets the buffer content number, of the BCN buffer. The Tacc is preferably less than the time that causes the communication or application to time-out (e.g. TCP/IP time-out).
Upon receiving the packet, the RNC keeps the packet in its buffer and resets its maximum inter-packet arrival timer, Timerint, and updates the BCN counter value. The RNC then compares the updated BCN counter value with a predetermined BCNX, the buffer size threshold for switching to Cell-DCH state. If the BCN counter value is less than BCNX, the RNC will wait for a next packet for the same recipient MS until Timerint expires. If the RNC receives a next packet for the recipient MS before Timerint expires, upon receiving the next packet, it again keeps this next packet, along with any previously accumulated ones, in its buffer, resets Timerint, updates the BCN counter value and compares BCN counter value with BCNX. The RNC repeats this process until any one of three conditions is met: (1) No further packet for the same recipient MS arrives before Timerint expires; (2) Timeracc expires; or (3) BCN counter value is greater than BCNX. In the case of (1) or (2), since the Cell-DCH switch criteria has not been triggered, the RNC will schedule the BS to send all accumulated packet(s) in its buffer to the recipient MS via FACH (Cell-FACH). In the case of (3), the Cell-DCH switch criteria is triggered, the RNC will send out a Physical Channel Reconfiguration message to instruct the recipient MS to switch to Cell-DCH and schedule the BS to send all accumulated packets in its buffer to the recipient MS via DCH or DSCH (Cell-DCH). Upon scheduling the delivery of any packets in the buffer from the BS to the MS, the RNC resets its BCN counter value to zero.
Upon delivery of the packets, the RCN will need to determine whether the MS should stay in its current state or switch to another state. The detailed description teaches a method for such determination, although the determination to switch states may be based on other conventional methods common in the art.
The RNC can detect if another packet has arrived for the recipient MS within Tinact ms. Tinact can be set to zero or any other values deemed appropriate. Tinact can also be a variable set to coincide with the end of the scheduled transmission of the accumulated packets. If there is not another packet for recipient MS within Tinact ms, the RNC will schedule a Physical Channel Reconfiguration message to instruct the recipient MS to release the DSCH and switch back to Cell-FACH state. Likewise, the buffer size also provides a way to measure congestion in the current channel. When the packet arrival rate exceeds the rate at which RNC can send out packets, packet accumulation will result in a large buffer. The RNC monitors the buffer content/size and when the buffer size exceeds a pre-determined threshold, the RNC will configure the BS to send the accumulated and scheduled packets via DCH.
Aspects of invention include methodologies for implementing such allocation of channel resources for packet transmissions based on traffic conditions, using the techniques outlined above. Other aspects of invention relate to networks and/or network controllers or other components for implementing those techniques.
Additional objects, advantages and novel features of the embodiments will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following and the accompanying drawings or may be learned by production or operation of the embodiments. The objects and advantages of the inventive concepts may be realized and attained by means of the methodologies, instrumentalities and combinations particularly pointed out in the appended claims.
The drawing figures depict preferred embodiments by way of example, not by way of limitations. In the figures, like reference numerals refer to the same or similar elements.
The subject matter disclosed involves a packet mode DCH/DCH+DSCH methodology for releasing the DCH resources associated with Cell-DCH state in a spread spectrum wireless communication network. The inventive access methodology accommodates bursty traffic in an optimum manner. Reference now is made in detail to the presently preferred embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals indicate like elements throughout the several views.
In a preferred embodiment (
With reference to the more detailed version shown in
The CDMA system provides a number of logically different channels for upstream and downstream communications over the air-link interface. Each channel is defined by one or more of the codes, for example the spreading code and/or the scrambling code. Several of the channels are common channels, but most of the channels are used for uplink or downlink packet communications between the base stations 13 and the mobile stations 15.
The RNC 11 measures traffic through the base stations 13 going to and from the mobile stations 15. In this way, the radio network controller (RNC) 11 monitors traffic demand in the illustrated network. The RNC 11 assigns physical channel resources to the mobile stations 15, by re-configuring the state of packet data connected mode of each mobile station 15 within each cell of each base station 13. Each mobile station 15 in packet data connected mode is either in Cell-FACH state or in Cell-DCH state.
As noted earlier, the Cell-DCH state includes two sub-states the DCH/DCH sub-state and the DCH/DCH+DSCH sub-state. In each sub-state, the mobile station (MS) 15 sends packet data via the Dedicated CHannel (DCH) uplink. The mobile station (MS) 15 tunes to receive downlink data, via either the DCH or the DCH+DSCH. In the downlink, the Radio Network Controller (RNC) 11 allocates either DCH or DCH+DSCH resources for packet data transmission. The Downlink Shared CHannel (DSCH) is a Physical Channel that provides a code-sharing mechanism in the downlink direction and is desirable when data traffic is bursty.
The Cell-FACH state also has two sub-states: the RACH/FACH sub-state and the CPCH/FACH sub-state. A mobile station in the CPCH/FACH sub-state is prepared to send packets via the CPCH while tuned in to the FACH for downlink messages. In the Cell-FACH state, the Radio Network Controller (RNC) 11 can allocate RACH or CPCH resources for uplink transmission.
In accord with the present access methodology, when the RNC 11 first receives packets for a mobile station (MS) from the core or from the packet network, the RNC allocates resources for their transmission. The RNC 11 buffers the first packet and resets two timers. One timer Timerint specifies the maximum inter-packet arrival time Tint, that is to say, the maximum time that the RNC 11 will wait between packets intended for one station 15 without transmitting. The other timer Timeracc specifies the maximum packet accumulation time Tacc, that is to say, the maximum time over which the RNC 11 will accumulate packets intended for one station 15 without transmitting. The RNC 11 also updates its buffer size denotes by the BCN counter value.
The BCN counter value is compared to BCNX, a predetermined threshold for switching to Cell-DCH state. If the BCN counter value exceeds BCNX, then the RNC 11 can proceed to immediate transmission of the accumulated packets to the recipient mobile station MS 15 by first switching the MS 15 to the Cell-DCH state.
The maximum packet accumulation timer Timeracc defines the time limit Tacc within which the network side components, e.g. the RNC and the base station, must transmit the oldest of the accumulated data. The Tacc is preferably less than the time that causes the communication or application to time-out (e.g. TCP/IP time-out). At the end of this time, the RNC 11 will initiate transmission of whatever packet or packets it has received from the core network 9 or the packet network 19 since the receipt of the first (oldest) packet in the buffer (and activation of the timers). The RNC 11 initiates transmission of the buffered packets for the particular station 15, on a first-in-first-out basis. The expiration of Timeracc causes the system to transmit using the Cell-FACH state.
The maximum inter-packet arrival time Tint, specified by the timer Timerint, defines a time limit to wait for new packets to arrive from the core network 9 or the packet network 19, intended for the particular mobile station 15. If no packets arrive, within this time interval, then the RNC 11 shall proceed to the immediate transmission of the buffered packet data to the recipient mobile station MS 15.
When no additional packets arrive for the same recipient MS within a Tint interval, the RNC 11 immediately sends all accumulated packet(s) in its buffer through base station (BS) 13 to the recipient MS 15 via FACH (Cell-FACH). However, if the RNC 11 receives a new packet, for the recipient MS, before timer Timerint expires, the RNC 11 adds that new packet to those previously accumulated in its buffer, resets Timerint, updates the value for the BCN counter, and waits again for the next packet. The RNC repeats this process until the limit Tacc for Timeracc expires. When Timeracc expires, the RNC 11 schedules the base station (BS) 13 to send all accumulated packets in its buffer to the recipient MS 14 via FACH.
If at anytime the updated BCN counter value exceeds BCNX, the RNC 11 sends a Physical Channel Reconfiguration message to instruct the recipient MS to switch back to Cell-DCH and then sends all accumulated packets in its buffer, to the recipient MS 14 via DCH or DSCH (Cell-DCH).
If the RNC 11 has scheduled transmission in the Cell-DCH state, the RNC preferably detects if there is another packet arriving for recipient MS within a period of Tinact ms, that is to say within a maximum inactivity interval. If there is no further packet for the recipient MS 15 within Tinact time, the RNC 11 schedules a Physical Channel Reconfiguration message to instruct the recipient MS to release the DSCH and switch back to Cell-FACH.
A preamble processor 316, pilot processor 317 and data-and-control processor 318 are coupled to the programmable-matched filter 315. A controller 319 is coupled to the preamble processor 316, pilot processor 317 and data-and-control processor 318. A de-interleaver 320 is coupled between the controller 319 and a forward-error-correction (FEC) decoder 321. The decoder 321 outputs data and signaling received via the UL channel to the MAC layer (not shown).
The BS spread-spectrum transmitter includes a forward-error-correction (FEC) encoder 322 coupled to an interleaver 323. A packet formatter 324 is coupled to the interleaver 323 and to the controller 319. A variable gain device 325 is coupled between the packet formatter 324 and a product device 326. A spreading-sequence generator 327 is coupled to the product device 326. A digital-to-analog converter 328 is coupled between the product device 328 and quadrature modulator 329. The quadrature modulator 329 is coupled to the local oscillator 313 and a transmitter RF section 330. The transmitter RF section 330 is coupled to the circulator 310.
The controller 319 has control links coupled to the analog-to-digital converter 314, the programmable-matched filter 315, the preamble processor 316, the digital-to-analog converter 328, the spreading sequence generator 327, the variable gain device 325, the packet formatter 324, the de-interleaver 320, the FEC decoder 321, the interleaver 323 and the FEC encoder 322.
A received spread-spectrum signal from antenna 309 passes through circulator 310 and is amplified and filtered by the receiver RF section 311. The local oscillator 313 generates a local signal, which the quadrature demodulator 312 uses to demodulate in-phase and quadrature phase components of the received spread-spectrum signal. The analog-to-digital converter 314 converts the in-phase component and the quadrature-phase component to digital signals. These functions are well known in the art, and variations to this block diagram can accomplish the same functions.
The programmable-matched filter 315 despreads the received spread-spectrum signal components. A correlator, as an alternative, may be used as an equivalent means for despeading the received spread-spectrum signal.
The preamble processor 316 detects a preamble portion of the received spread-spectrum signal. The pilot processor 317 detects and synchronizes to a pilot portion of the received spread-spectrum signal. The data and control processor 318 detects and processes the data portion of the received spread-spectrum signal. Detected data passes through the controller 319 to the de-interleaver 320 and FEC decoder 321. Data and signaling from the up-link are outputted from the FEC decoder 321 to the higher layer elements in or associated with the BS 13 and through the link to the RNC 11.
The RNC 11 supplies data and signaling over a link to the base station. In the BS transceiver, the MAC layer elements supply data and signaling information, intended for down-link transmission, to the input of the FEC encoder 322. The signaling and data are FEC encoded by the FEC encoder 322, and interleaved by the interleaver 323. The packet formatter 324 formats data, signaling, acknowledgment signal, collision detection signal, pilot signal and transmitting power control (TPC) signal into appropriate packets. Each packet is outputted from the packet formatter 324, and the packet level is amplified or attenuated by the variable gain device 325. The packet is spread-spectrum processed by the product device 326, with a spreading chip-sequence from the spreading-sequence generator 327. The packet is converted to an analog signal by the digital-to-analog converter 328, and in-phase and quadrature-phase components are generated by the quadrature modulator 329 using a signal from local oscillator 313. The modulated down-link packet is translated to a carrier frequency, filtered and amplified by the transmitter RF section 330, and then it passes through the circulator 310 and is radiated by antenna 309.
An acknowledgment detector 416, pilot processor 417 and data-and-control processor 418 are coupled to the programmable-matched filter 415. A controller 419 is coupled to the acknowledgment detector 416, pilot processor 417 and data-and-control processor 418. A de-interleaver 420 is coupled between the controller 419 and a forward-error-correction (FEC) decoder 421. The decoder 421 outputs data and signaling received via the DL channel to the MAC layer elements (not shown) of the MS.
The MS spread-spectrum transmitter includes a forward-error-correction (FEC) encoder 422 coupled to an interleaver 423. A packet formatter 424 is coupled through a multiplexer 451 to the interleaver 423. The packet formatter 424 also is coupled to the controller 419. A preamble generator 452 and a pilot generator 453 are coupled to the multiplexer 451. A variable gain device 425 is coupled between the packet formatter 424 and a product device 426. A spreading-sequence generator 427 is coupled to the product device 426. A digital-to-analog converter 428 is coupled between the product device 428 and quadrature modulator 429. The quadrature modulator 429 is coupled to the local oscillator 413 and a transmitter RF section 430. The transmitter RF section 430 is coupled to the circulator 410.
The controller 419 has control links coupled to the analog-to-digital converter 414, the programmable-matched filter 415, the acknowledgment detector 416, the digital-to-analog converter 428, the spreading sequence generator 427, the variable gain device 425, the packet formatter 424, the de-interleaver 420, the FEC decoder 421, the interleaver 423, the FEC encoder 422, the preamble generator 452 and the pilot generator 453.
A received spread-spectrum signal from antenna 409 passes through circulator 410 and is amplified and filtered by the receiver RF section 411. The local oscillator 413 generates a local signal, which the quadrature demodulator 412 uses to demodulate in-phase and quadrature phase components of the received spread-spectrum signal. The analog-to-digital converter 414 converts the in-phase component and the quadrature-phase component to digital signals. These functions are well known in the art, and variations to this block diagram can accomplish the same functions.
The programmable-matched filter 415 despreads the received spread-spectrum signal components. A correlator, as an alternative, may be used as an equivalent means for despeading the received spread-spectrum signal.
The acknowledgment detector 416 detects certain acknowledgments in the received spread-spectrum signal. The pilot processor 417 detects and synchronizes to a pilot portion of the received spread-spectrum signal. The data and control processor 418 detects and processes the data portion of the received spread-spectrum signal. Detected data passes through the controller 419 to the de-interleaver 420 and FEC decoder 421. Data and signaling from the DL are outputted from the FEC decoder 421 to the higher level elements in or associated with the MS 15.
In the MS transceiver, the MAC layer elements supply data and signaling information intended for transmission over the up-link channel, to the input of the FEC encoder 422. Data and signaling information are FEC encoded by FEC encoder 422, and interleaved by interleaver 423. The preamble generator 452 generates a preamble, and the pilot generator 453 generates a pilot for the preamble. The multiplexer 451 multiplexes the data, preamble and pilot, and the packet formatter 424 formats the preamble, pilot and data into a common-packet channel packet. Further, the packet formatter 424 formats data, signaling, acknowledgment signal, collision detection signal, pilot signal and TPC signal into a packet. The packet formatter 424 outputs the packet, and the packet level is amplified or attenuated by variable gain device 425. The packet is spread-spectrum processed by product device 426, with a spreading chip-sequence from spreading-sequence generator 427. The packet is converted to an analog signal by digital-to-analog converter 428, and quadrature modulator 429 using a signal from local oscillator 413 generates in-phase and quadrature-phase components. The modulated up-link packet is translated to a carrier frequency, filtered and amplified by the transmitter RF section 430 and then it passes through the circulator 430 and is radiated by the antenna 409.
U.S. Pat. No. 6,169,759 to Kanterakis et al. issued Jan. 2, 2001 provides a more detailed description of the operation of the PHY transceivers shown in
Assume for example, that the RNC 11 received the first four packets, as shown to the left on line (a) of
The timers may be implemented in any convenient manner. For example, any of the timers used herein can use a downcount approach, that is to say reset to maximum and downcount to zero. Any of the timers may alternatively implement an up-count approach, where the timer is reset to 0 and counts up to a maximum or threshold value. The timers could be analog, but preferably are implemented as digital logic, as part of the RNC application program.
In the process flow of
In this first illustrated example (first part of
The RNC will use the Cell-DCH state only when the BCN counter value exceeds BCNX and when it has received packets and the MSn is still in the Cell-DCH state. In this case, assuming the MSn was in the Cell-FACH state, the first four pulses received by the RNC (
In the next example shown in
In this embodiment, the RNC 11 also implements an inactivity timer Timerinact. If further packets are received before Timerinact expires, the new packets are transmitted while still in the Cell-DCH transmission. In continuing with this second example, after the first six packets in the buffer are transmitted, the inactivity timer Timerinact does not expire before more packets destined for this mobile station 15 arrive. Thus, the RNC will transmit the remaining four packets while in the Cell-DCH state.
A decision is made in Step S61 (in
In the third illustrated example in
Upon receiving a packet, the RNC 11 loads the packet into its buffer and updates the BCN counter value accordingly.
In the embodiment of
In the embodiment of
If the buffer size value kept in the BCN counter exceeds BCNX, the Cell-DCH switch criteria is triggered, therefore the RNC will send out a Physical Channel Reconfiguration message (if necessary) to instruct the recipient MS to switch to Cell-DCH. The RNC next schedules the BS to send all accumulated packets in its buffer to the recipient MS via DCH or DSCH (Cell-DCH). In the embodiment of
In the embodiment of
As noted, the initial steps in the embodiment of
If the RNC receives a next packet for the recipient MS before Timerint expires, upon receiving the next packet, it again stores this next packet, along with any previously accumulated ones, in its buffer, resets the Timerint, updates the BCN counter value and checks the BCN counter value and the timer Timeracc. Again, the RNC repeats this process until any one of three conditions is met: (1) No further packet for the same recipient MS arrives before Timerint expires; (2) Timeracc expires; or (3) BCN counter value is greater than BCNX.
It is contemplated that some implementations will use Timeracc as the criteria to switch to Cell-DCH transmission. In such an embodiment, if after buffering one or more packets, the accumulation timer Timeracc expires, the RNC will send out a Physical Channel Reconfiguration message (if necessary) to instruct the recipient MS to switch to Cell-DCH.
However, in the illustrated embodiment, the RNC checks the transmission state and the Timeracc state. If not already in the Cell-DCH state and the Timeracc has not expired, the RNC checks the BCN counter value. If that value exceeds the threshold BCNX, the RNC next schedules the BS to send all accumulated packets in its buffer to the recipient MS via DCH or DSCH (Cell-DCH). In the embodiment of
In either embodiment (
In the embodiments, the state control processing was implemented in the radio network controller (RNC) 11. The RNC 11 may be implemented as a separate packet switching node in the network, which has sufficient processing capability that is programmed to detect conditions and provide instructions to the base stations, in the manner outlined above. Such an RNC node can be implemented with a general purpose programmable device having the appropriate packet interfaces for the necessary communications and sufficient processing and memory capacity necessary to perform the necessary routing and control functions. Such a device is then programmed with the executable code to implement the desired one of the processing embodiments, as part of its programming to implement its other channel allocation and routing functions in the context of the CDMA network.
The term radio network controller or RNC as used herein refers to a control functionality or application, for monitoring packet traffic and assigning radio-link resources through control of the base stations. As shown in the drawings and described above, the exemplary RNC 11 may take the form of a physically separate node between the core network and a number of base stations within one radio network system. Those skilled in the art will recognize, however, that the control functionality of the RNC may actually reside at any convenient network location or locations. For example, the RNC functionality may be combined with that of one or a distributed number of the base stations. Alternatively, the RNC functionality may be implemented in a higher-level network node, for example within another layer of controller.
While the foregoing has described what are considered to be the best mode and/or other preferred embodiments, it is understood that various modifications may be made therein and that the invention or inventions disclosed herein may be implemented in various forms and embodiments, and that they may be applied in numerous applications, only some of which have been described herein. It is intended by the following claims to claim any and all modifications and variations that fall within the true scope of the inventive concepts.
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|U.S. Classification||370/235, 370/335|
|International Classification||H04B7/216, H04J1/16|
|Cooperative Classification||H04L12/5693, H04L47/6255, H04L47/30, H04L47/56, H04L47/14|
|European Classification||H04L12/56K, H04L47/14, H04L47/62G1, H04L47/56, H04L47/30|