The invention relates to a method, to a mesh node, to a mesh network, to a transceiver, and to a computer-readable program distribution medium.
Duplexing designs for future broadband access have recently been studied extensively. A document “Duplex arrangement for future broadband radio interfaces” IST-2003-507581 WINNER D2.5 v1.0 studies different relay duplexing mechanisms. As to mesh and relay use, the above document concentrates on Time Domain Duplexing (TDD) and Half-Duplex Frequency Domain Duplexing (FDD) for the relaying designs.
According to the above document, TDD is advantageous in handling traffic symmetries, in supporting multihop applications, and preferable in case of direct link, i.e. terminal-to-terminal, communications. Moreover, the document relies on transmission on unpaired bands, which may facilitate the search for spectrum for broadband communications. However, TDD requires synchronization and coordination between different operators assigned to adjacent carriers, unless spatial decoupling and/or interference avoidance techniques can guarantee sufficiently low levels of crosslink (uplink-to-downlink and downlink-to-uplink) interference. In this respect, Half Duplex FDD has an advantage over TDD, especially in cellular wide area coverage scenarios. FDD has not been considered for mesh networks because multiple transceivers would be required to transmit and receive simultaneously.
One of the assumptions in future next generation designs is that an RN-to-RN radio for mesh is different from RN-to-MN client access radios. Reason for this is that the properties of the mesh network ad client access are different. Mesh radios are more “equivalent” with each other and need to manage the radio resources collectively. A client access radio, however, is connected only to a single access point (RN/AG), thus the access point behaves like a traditional base station from the point of view of the mobile node.
In mesh data forwarding, very low delay and low jitter connections between the relay nodes are required. This is needed for applications requiring low delay running over the mesh networks. Further, in mesh networks relay nodes are actively connected to a limited amount of other relay nodes. Usually such a connection is provided only to the nearest relay node, which then forwards the traffic to the next node.
An object of the invention is to provide an improved method, a mesh node, a mesh network, a transceiver, and a computer-readable program distribution medium.
According to an aspect of the invention, there is provided a method comprising: providing two transmission bands for simultaneous communication of signals by a plurality of mesh nodes of a mesh network; dividing both of the transmission bands into at least three subchannel regions, each subchannel region including a subset of available logical subchannels of a multiple access technology; and allocating at least four subchannel regions of the transmission bands to each mesh node of the plurality of mesh nodes for use in transmission and reception, wherein the transmission and reception of a mesh node are allocated to subchannel regions of different transmission bands.
According to another aspect of the invention, there is provided a mesh node comprising: a processing unit for controlling functions of the mesh node; and a transceiver for simultaneous communication of signals with one or more other mesh nodes of a mesh network using two transmission bands, wherein both of the two transmission bands include at least three subchannel regions, each subchannel region including a subset of available logical subchannels of a multiple access technology. The processing unit is configured to control use of at least four subchannel regions allocated to the mesh node for transmission and reception, wherein the transmission and reception of the mesh node are allocated to subchannel regions of different transmission bands.
According to another aspect of the invention, there is provided a mesh network comprising a plurality of mesh nodes according to claim 5.
According to another aspect of the invention, there is provided a transceiver for a mesh node, the transceiver comprising: a transmitter for transmitting signals in at least one subchannel region of at least three subchannel regions of a transmission band of two transmission bands allocated to a plurality of mesh nodes of a mesh network for simultaneous communication of signals, each subchannel region including a subset of available logical subchannels of a multiple access technology; and a receiver for receiving signals in at least one subchannel region of at least three subchannel regions of a transmission band of the two transmission bands other than that the transmitter is using for transmitting. The transceiver is configured to control use of at least four subchannel regions allocated to the mesh node for transmission and reception.
According to another aspect of the invention, there is provided a computer-readable program distribution medium encoding a computer program of instructions for executing a computer process, the process comprising: providing two transmission bands for simultaneous communication of signals by a plurality of mesh nodes of a mesh network; dividing both of the transmission bands into at least three subchannel regions, each subchannel region including a subset of available logical subchannels of a multiple access technology; and allocating at least four subchannel regions of the transmission bands to each mesh node of the plurality of mesh nodes for use in transmission and reception, wherein the transmission and reception of a mesh node are allocated to subchannel regions of different transmission bands.
According to another aspect of the invention, there is provided a mesh node comprising: transceiver means for simultaneous communication of signals with one or more other mesh nodes of a mesh network using two transmission bands, wherein both of the two transmission bands include at least three subchannel regions, each subchannel region including a subset of available logical subchannels of a multiple access technology, and processing means for controlling use of at least four subchannel regions allocated to the mesh node for transmission and reception, wherein the transmission and reception of the mesh node are allocated to subchannel regions of different transmission bands.
According to another aspect of the invention, there is provided a transceiver for a mesh node, the transceiver comprising: transmitting means for transmitting signals in at least one subchannel region of at least three subchannel regions of a transmission band of two transmission bands allocated to a plurality of mesh nodes of a mesh network for simultaneous communication of signals, each subchannel region including a subset of available logical subchannels of a multiple access technology; receiving means for receiving signals in at least one subchannel region of at least three subchannel regions of a transmission band of the two transmission bands other than that the transmitter is using for transmitting; and processing means for controlling use of at least four subchannel regions allocated to the mesh node for transmission and reception.
The invention provides several advantages.
A flexible subchannel reuse mechanism in mesh networks is provided. Frequency division duplexing can now be used in mesh networks. Packet forwarding delays are minimized since all mesh nodes are able to transmit simultaneously. There is no need to use guard times. The whole mesh network can forward traffic simultaneously.
In the following, the invention will be described in greater detail with reference to the embodiments and the accompanying drawings, in which
With reference to
In an embodiment, two transmission bands are provided in the mesh network for simultaneous communication of signals by a plurality of mesh nodes of the mesh network. The transmission bands are divided into at least three subchannel regions, each subchannel region including a subset of available logical subchannels of a multiple access technology. At least four subchannel regions of the transmission bands are allocated to each mesh node 103 of the plurality of mesh nodes for use in transmission and reception.
In an embodiment, the transmitter 204 is configured to transmit signals in at least one subchannel region of the at least three subchannel regions allocated to the mesh node. The receiver 206 is configured to receive signals in at least one subchannel region of the at least three subchannel regions of a transmission band of the two transmission bands other than that the transmitter is using for transmitting. The processing unit 200 is configured to control use of at least four subchannel regions allocated to the mesh node for transmission and reception.
In an embodiment, a mesh network with frequency division duplexing is provided by using just two transmission bands (or channels), such that different reuse factors can easily be designed within these bands. This enables subchannelization within a transmission band, together with FDD duplexing, in a mesh network. One mechanism for creating subchannelization within a transmission band is orthogonal frequency division multiple access (OFDMA). In the following embodiments, mesh radios using OFDMA are presented as examples. The same principle can, however, be applied to any radio systems using subchannelization for resource allocation. For example, according to an embodiment where dual carrier FDD frequency reuse concept uses code division multiplexing (CDMA) instead of OFDMA, then the subchannel regions would refer to code regions.
An example of a transmitter is illustrated in
Orthogonal frequency division multiple access (OFDMA) is a mechanism for creating frequency division multiple access (FDMA) by using OFDM. In an OFDMA transmitter, the useful part of the subcarriers 0 to N−1 of an OFDMA signal is divided into a number of K logical subchannels. These subchannels can then be assigned to different users. The subcarriers belonging to a logical subchannel can either be distributed over the whole useful band giving a high amount of frequency diversity or packed together for enabling interference control mechanisms and frequency domain scheduling with low frequency diversity.
In the example of
In an embodiment, two transmission bands B0 and B1 are provided for simultaneous communication of signals by the plurality of mesh nodes NODE 0 to NODE 7 of the mesh network. The transmission bands B0 and B1 are divided into at least three subchannel regions (0, 1, 2), each subchannel region including a subset of available logical subchannels of a multiple access technology. Further, at least four subchannel regions, i.e. frequency regions in this OFDMA related example, of the transmission bands are allocated to each mesh node of the plurality of mesh nodes for use in transmission and reception, and the transmission and reception of a mesh node are allocated to subchannel regions of different transmission bands.
Dual carrier FDD requires use of two transmission bands B0 and B1 of bandwidth B separated far enough in duplex frequency for enabling a mesh node to transmit in one channel and to receive in another channel. The use of these transmission bands B0 and B1 for transmission and reception varies from hop to hop.
The two transmission bands B0 and B1 are internally divided into at least three non-overlapping subchannel regions, i.e. frequency regions in this OFDMA example. For simplicity, in
In the example of
In the example of
Although in
In
In an embodiment, each mesh node is capable of simultaneously transmitting data to one or more neighboring mesh nodes in a first transmission band B0, and receiving data from one or more neighboring mesh nodes in a second transmission band B1. Further, each mesh node is capable of transmitting data simultaneously to one or more first neighboring mesh nodes in an uplink direction and to one or more second neighboring mesh nodes in a downlink direction in two or more subchannel regions of each transmission band B0, B1. The mesh nodes are also capable of receiving data simultaneously from one or more first neighboring mesh nodes from a downlink direction and from one or more second neighboring mesh nodes from an uplink direction in two or more subchannel regions of a transmission band B0 or B1.
In an embodiment, a mesh node can communicate with other mesh nodes about available resources that the mesh node may not need at the time. Then, this unused resource can be used by another mesh node. For example, if NODE 1 has nothing to transmit in T1.1 to NODE 0, then NODE 3 may use T1.1 transmission to NODE 2.
Dual carrier FDD is a practical mechanism to create 1/3 and also lower frequency reuses using two transmission bands.
In an embodiment, time division duplexing (TDD) can be added on top of OFDMA so as to achieve a higher granularity allocating capacity for different users. The same principle can be applied to creating other (higher) frequency reuse factors.
The embodiments of the invention may be realized in transceiver, comprising a controller. The controller may be configured to perform at least some of the steps described in connection with the flowchart of
The computer program may be stored on a computer program distribution medium readable by a computer or a processor. The computer program medium may be, for example but not limited to, an electric, magnetic, optical, infrared or semiconductor system, device or transmission medium. The computer program medium may include at least one of the following media: a computer readable medium, a program storage medium, a record medium, a computer readable memory, a random access memory, an erasable programmable read-only memory, a computer readable software distribution package, a computer readable signal, a computer readable telecommunications signal, computer readable printed matter, and a computer readable compressed software package.
Even though the invention has been described above with reference to an example according to the accompanying drawings, it is clear that the invention is not restricted thereto but it can be modified in several ways within the scope of the appended claims.
Number | Date | Country | Kind |
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20065811 | Dec 2006 | FI | national |