The invention relates to the field of wireless telecommunications and, particularly, to communication between service groups or service sets in a wireless communication system.
Wireless Local Area Network (WLAN) has undergone vast development in order to increase throughput. Task groups such as 802.11b, 802.11a, 802.11g and 802.11n have demonstrated continuous improvement of the WLAN radio throughput. 802.11ac is another task group that is developing the WLAN radios that operate at a frequency spectrum below 6 GHz and especially at 5 GHz. There exist other task groups within the IEEE 802.11 standardization.
According to an aspect of the present invention, there are provided methods as specified in claims 1 and 6.
According to another aspect of the present invention, there are provided apparatuses as specified in claims 13 and 18.
According to another aspect of the present invention, there is provided an apparatus as specified in claim 26.
According to yet another aspect of the present invention, there is provided a computer program product embodied on a computer readable distribution medium as specified in claim 27. According to yet another aspect, there is provided a computer-readable distribution medium comprising the computer program product.
Embodiments of the invention are defined in the dependent claims.
Embodiments of the present invention are described below, by way of example only, with reference to the accompanying drawings, in which
The following embodiments are exemplary. Although the specification may refer to “an”, “one”, or “some” embodiment(s) in several locations, this does not necessarily mean that each such reference is to the same embodiment(s), or that the feature only applies to a single embodiment. Single features of different embodiments may also be combined to provide other embodiments. Furthermore, words “comprising” and “including” should be understood as not limiting the described embodiments to consist of only those features that have been mentioned and such embodiments may contain also features/structures that have not been specifically mentioned.
A general architecture of a wireless telecommunication system to which embodiments of the invention may be applied is illustrated in
The 802.11n specifies a data transmission mode that includes 20 MHz wide primary and secondary channels. The primary channel is used in all data transmissions, and with clients supporting only the 20 MHz mode. A further definition in 802.11n is that the primary and secondary channels are adjacent. The 802.11n specification also defines a mode in which a STA can have only one secondary channel which results in a maximum bandwidth of 40 MHz. IEEE 802.11ac task group extends such an operation model to provide for wider bandwidths by increasing the number of secondary channels from 1 up to 7, thus resulting in bandwidths of 20 MHz, 40 MHz, 80 MHz, and 160 MHz.
As mentioned above, the transmission band of a BSS contains the primary channel and zero or more secondary channels. The secondary channels may be used to increase data transfer capacity of the TXOP. The secondary channels may be called a secondary channel, a tertiary channel, a quaternary channel, etc. The primary channel may be used for channel contention, and a transmission opportunity (TXOP) may be gained after successful channel contention on the primary channel. Every STA is reducing a backoff value while the primary channel is sensed to be idle for a certain time interval, for instance 9 microseconds. When the backoff reaches zero, the STA gains the TXOP and starts transmission. If another STA gains the TXOP before that, the channel sensing is suspended, and the STA proceeds with the channel sensing after the TXOP of the other STA has ended. The time duration (the backoff factor) may not be reset at this stage, and the time duration that already lapsed before the suspension is also counted, which means that the STA now has a higher probability of gaining the TXOP. A secondary channel may be used in the transmission if it has been free for a determined time period (may be the same or different time period than that used for gaining the TXOP) just before TXOP start time in order for the contending STA to take the secondary channel in use.
A virtual carrier sensing function is provided by the provision of a network allocation vector (NAV) which is used to reserve a channel. Most of the transmitted frames comprise a duration field which can be used to reserve the medium (or provide duration of the NAV protection) for the duration indicated by the value of the duration field. In practice, the NAV is a timer that indicates the amount of time the medium will be reserved. In a typical operation, the transmitting and receiving stations (STAs) will set the NAV to the time for which they expect to use the medium while other STAs count down from the NAV to zero before starting the channel contention. The virtual carrier sensing function indicates that the medium is busy when NAV is non-zero and idle when NAV is zero. The NAV may be set to protect frames communicated on the primary channel of the BSS.
Referring back to
Referring to
Referring to
As mentioned above, the primary channel of the second BSS (the BSS of the proxy apparatus) may be located on the channel set of the first BSS, and the RTS message may be transmitted to the proxy apparatus on the channels of the first BSS including the primary channel of the second BSS. In such embodiments, both the TXOP holder and the proxy apparatus may operate only on the channels of their respective BSSs, and the proxy apparatus may respond with the CTS message only on its primary channel and, optionally, on any auxiliary channel queried in the transmission request message that is common to both BSSs. The RTS message sets the NAV on both primary channels, and the CTS message may be used to verify the existence of the RTS NAV and indicate that the primary channel of the second BSS is available for the data transmission. In other embodiments where the primary channel of the second BSS is outside the frequency channels of the first BSS, the TXOP holder may identify in block 202 also the primary channel of the second BSS and transmit the RTS message to the proxy apparatus on the primary channel of the second BSS.
Let us now consider some embodiments for initializing the proxy selection and proxy operation with reference to
The Element ID is set to unique value as specified in 802.11ac.
The length of the field is set to the size of the information element excluding the Element ID and Length fields.
The number of Proxy Elements field is an unsigned integer and set to the number of Proxy Candidate elements. Each proxy candidate element may have the following structure:
Offset of Primary Channels indicates the offset between the primary channels of the first and the second BSS, and it may be a signed integer (the sign indicating the direction of the offset) utilizing the channel numbering, e.g. one illustrated in
Upon reception of the request message from the AP, the STA may carry out a proxy selection process in S2. In the proxy selection process, the STA may be configured to select at least one of the proxy candidates. The selection may be made based on channel sounding on at least one of the overlapping channels so as to detect a transmission from any one of the proxy candidates. The STA may be configured to monitor for a physical layer convergence protocol (PLCP) header comprised at the head of every transmission. The PLCP header or a MAC header associated with the PLCP header may comprise an identifier of its transmitter and, thus, it enables the STA to determine whether the transmitted is one of the proxy candidates by analyzing the PLCP header and/or the MAC header. The STA may select one of the candidate proxies it is able to detect. The STA may also prioritize the proxy candidates, e.g. an AP proxy may be preferred.
In S3, the STA transmits a proxy selection response message to the AP, indicating the selected proxy candidate. The proxy selection response message may include the MAC address of the selected proxy as shown in the following exemplary format in the proxy selection response message:
Upon detection of no proxy candidate, the STA may set the MAC address field of the proxy selection response message to zero. Then, the AP may reiterate the process of
In another embodiment, the AP (or a mesh STA or another apparatus of the first BSS) indicates a proxy apparatus the AP itself currently uses. Referring to
The proxy indication message may include the MAC address of at least one proxy the AP currently uses and the proxy indication message may be comprised in a beacon frame transmitted periodically by the AP and/or in a Probe Response message transmitted in response to a Probe Request message received from the STA. Upon reception of the proxy indication message, the STA may derive the MAC address of the proxy apparatus from the proxy indication message and start using the proxy apparatus by addressing the RTS messages to it prior to a data transmission.
It should be noted that a plurality of proxy apparatuses may be selected. The STA may select a proxy apparatus for every receiver apparatus to which it transmits data, and such a set of proxy apparatuses may include multiple proxies. A different proxy apparatus may be selected for different receivers, or the same proxy may be used for multiple receivers. Moreover, the different proxies may be even in different BSSs all having the overlapping frequency spectrum with the first BSS. Still further, the STA may use a different proxy apparatus when transmitting data to the AP from the proxy used when transmitting data to another STA of the first BSS. The proxy to use with the AP may be selected to be the same proxy the AP uses, while another criterion may be used for selecting a proxy for the STA-STA data transmissions.
Let us now consider signaling with respect to initiating the proxy operation between a transmitter apparatus of the first BSS (STA or AP), and the proxy apparatus of the second BSS. Referring the
The request message may define the offset between the primary channels and a type of the STA transmitting the request. The octet of the Type field may have the following bit format:
Each bit may be set to one value when the corresponding operation mode is currently applied by the STA (e.g. 1), and set to the other value (e.g. 0) otherwise.
Upon reception of the request message having the information elements of Table 4, the proxy apparatus may process the request and determine whether or not it can approve the request. The proxy apparatus may check, for example, the number of apparatus with which it currently provides the proxy service with respect to the maximum number of serviced apparatuses. Other criteria may also be used when determining whether or not to approve the request. Upon determining the result of the check, the proxy apparatus transmits in S22 a proxy operation response message to the transmitter, wherein the response message indicates whether or not the request of S21 was approved or denied. Upon reception of the approval, the transmitter starts to utilize the proxy apparatus and, otherwise, the transmitter may try to request another proxy apparatus to operate as the proxy for the transmitter. The operation of
With respect to the control messages related to the initializing the proxy operation, correct reception of any message may be acknowledged by an acknowledgment message.
Upon successful proxy initiation and gaining the TXOP, the transmitter apparatus (the TXOP holder) may be configured to transmit the RTS messages at least to the proxy apparatus before the data transmission so as to protect the data transmission in both the first BSS and the second BSS. Let us consider embodiments of such a process with reference to
Upon reception of the RTS message, the proxy apparatus may first evaluate whether or not the channels queried with the RTS are free. This may include the clear-channel assessment (CCA) in which the proxy apparatus scans the channel(s) for a determined time period so as to detect ongoing radio transmissions. It may also (or alternatively) include determination of current NAV protections on the queried channels, at least the primary channel of the second BSS. Upon detection of no other transmissions, the proxy apparatus may transmit the CTS message to the TXOP holder (the CTS message may include only the receiver address field without a transmitter address field) on the channels queried with the RTS message and detected to be available for the data transmission.
The NAV protection gained by the RTS transmission to the proxy apparatus may extend to protect a subsequent transmission by the TXOP holder, as illustrated in
After the RTS/CTS handshake with the proxy apparatus(es), the procedure may be similar to that of
Let us now describe criteria related to the transmission of the CTS message from the proxy apparatus upon reception of the RTS message and upon carrying out the CCA and/or NAV detection. A static and a dynamic reservation type may be defined, wherein the static reservation type may refer to proceeding with the data transmission if all the channels indicated in the RTS message are detected as free also by the proxy apparatus. The dynamic reservation type may refer to proceeding with the transmission when a subset of the channels indicated in the RTS message is detected to be free by the proxy apparatus. The reservation type may be indicated in the RTS message. With respect to the dynamic and/or static reservation type, a minimum number of free channels needed to carry out the data transmission may be defined in the RTS message, or it may be defined as a default value in the proxy apparatus, e.g. the number of free channels in the receiver with respect to the number free channels on which the RTS was received. For instance, if the RTS message has commanded the proxy apparatus to apply the static reservation type, e.g. all or a given subset of the queried resources need to be free to proceed with the data transmission, the proxy apparatus may transmit the CTS frame only if all the queried channels are sensed to be idle. If the RTS message commands the dynamic reservation type, e.g. command to reserve any available resource, the proxy apparatus may determine that the TXOP proceeds to the data transmission if any or a given subset of channels is free. If the subset of channels is free, the proxy apparatus transmits the CTS message on the free channels, including the primary channel(s).
The proxy apparatus may be configured to discriminate the RTS messages received from a transmitter of own BSS from RTS messages received from a transmitter of another BSS, and determine the channels on which to transmit the CTS accordingly. For example, the proxy apparatus may monitor only for its primary channel for the RTS messages, while it may have to transmit the CTS message only on the monitored primary channel or also on the primary channel of the other BSS outside the monitored channels.
The apparatus may comprise a communication controller circuitry 10 configured to control the communications in the communication apparatus. The communication controller circuitry 10 may comprise a control part 14 handling control signaling communication with respect to transmission, reception, and extraction of control frames including the transmission request messages and the transmission response messages, as described above. The communication controller circuitry 10 may further comprise a data part 16 that handles transmission and reception of payload data during transmission opportunities of the communication apparatus (transmission) or transmission opportunities of other communication apparatuses (reception). The communication controller circuitry 10 further comprise a proxy operation circuitry 11 configured to carry out the above-described functionalities of the proxy apparatus and/or the TXOP holder selecting the proxy apparatus and communicating with the proxy apparatus.
The circuitries 11 to 16 of the communication controller circuitry 10 may be carried out by the one or more physical circuitries or processors. In practice, the different circuitries may be realized by different computer program modules. Depending on the specifications and the design of the apparatus, the apparatus may comprise some of the circuitries 11 to 16 or all of them.
The apparatus may further comprise the memory 20 that stores computer programs (software) configuring the apparatus to perform the above-described functionalities of the communication device. The memory 20 may also store communication parameters and other information needed for the wireless communications. The apparatus may further comprise radio interface components 30 providing the apparatus with radio communication capabilities within the BSS and with other BSSs. The radio interface components 30 may comprise standard well-known components such as amplifier, filter, frequency-converter, (de)modulator, and encoder/decoder circuitries and one or more antennas. The apparatus may further comprise a user interface enabling interaction with the user of the communication device. The user interface may comprise a display, a keypad or a keyboard, a loudspeaker, etc.
In an embodiment, the apparatus carrying out the embodiments of the invention in the communication apparatus comprises at least one processor and at least one memory including a computer program code, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to carry out the steps of any one of the processes of
As used in this application, the term ‘circuitry’ refers to all of the following: (a) hardware-only circuit implementations, such as implementations in only analog and/or digital circuitry, and (b) to combinations of circuits and software (and/or firmware), such as (as applicable): (i) a combination of processor(s) or (ii) portions of processor(s)/software including digital signal processor(s), software, and memory(ies) that work together to cause an apparatus to perform various functions, and (c) to circuits, such as a microprocessor(s) or a portion of a microprocessor(s), that require software or firmware for operation, even if the software or firmware is not physically present.
This definition of ‘circuitry’ applies to all uses of this term in this application. As a further example, as used in this application, the term “circuitry” would also cover an implementation of merely a processor (or multiple processors) or portion of a processor and its (or their) accompanying software and/or firmware. The term “circuitry” would also cover, for example and if applicable to the particular element, a baseband integrated circuit or applications processor integrated circuit for a mobile phone or a similar integrated circuit in server, a cellular network device, or other network device.
The processes or methods described in
The present invention is applicable to wireless telecommunication systems defined above but also to other suitable telecommunication systems. The protocols used, the specifications of mobile telecommunication systems, their network elements and subscriber terminals, develop rapidly. Such development may require extra changes to the described embodiments. Therefore, all words and expressions should be interpreted broadly and they are intended to illustrate, not to restrict, the embodiment. It will be obvious to a person skilled in the art that, as technology advances, the inventive concept can be implemented in various ways. The invention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.
Number | Date | Country | Kind |
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20115163 | Feb 2011 | FI | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/FI2012/050079 | 1/30/2012 | WO | 00 | 7/18/2013 |