Patent Application
20080080440
Aspects, features and advantages of embodiments of the present invention will become apparent from the following description of the invention in reference to the appended drawing in which like numerals denote like elements and in which:
While the following detailed description may describe example embodiments of the present invention in relation to wireless local area networks (WLANs) and related devices, the inventive embodiments are not limited thereto and can be applied to other types of wireless networks and devices where similar advantages may be obtained. Such networks for which inventive embodiments may be applicable specifically include, wireless personal area networks (WPANs), wireless metropolitan area networks (WMANs) and/or wireless wide area networks (WWANs). Additionally, embodiments of the present invention may be specifically related to devices using a combination of WLAN, WMAN and/or WWAN over-the-air (OTA) protocols.
The following inventive embodiments may be used in a variety of applications including transmitters and receivers of a radio system. Radio systems specifically included within the scope of the present invention include, but are not limited to, network interface cards (NICs), network adaptors, mobile stations, base stations, access points (APs), hybrid coordinators (HCs), gateways, bridges, hubs and routers. Further, the radio systems within the scope of the invention may include cellular radiotelephone systems, satellite systems, personal communication systems (PCS), two-way radio systems and two-way pagers as well as computing devices including radio systems such as personal computers (PCs) and related peripherals, personal digital assistants (PDAs), personal computing accessories and all existing and future arising systems which may be related in nature and to which the principles of the inventive embodiments could be suitably applied.
Wireless mesh systems are the focus of several current standardization efforts. For example, the Institute of Electrical and Electronics Engineers (IEEE) 802.11s Mesh Task Group (TG) is actively working on standard solutions for WLAN mesh networking. Additionally, the IEEE 802.16j Mobile Multi-hop Relay (MMR) task group is also evaluating solutions for standardization in furtherance of the IEEE 802.16j project approval request (PAR) (Approved: Mar. 30, 2006) for wireless broadband access (WBA) networks. Embodiments of the present invention may be compatible with one or more of the physical layer (PHY) and/or medium access control (MAC) layer protocols defined by these and/or other IEEE 802.x wireless standards although the inventive embodiments are not limited in this respect. Additionally or alternatively, embodiments of the present invention may use protocols compatible with other wireless standards and/or cellular protocols such as general packet radio service (GPRS), various generations of code division multiple access (CDMA) including wideband CDMA (WCDMA), 3rd Generation Partnership Project (3GPP) and similar WWAN protocols.
Multi-hop (or mesh) routing and cooperative diversity (e.g., distributed multiple-input multiple-output (MIMO)) are two technique proposed for use in various wireless networks (e.g., data exchange networks and sensor networks). These techniques allow communication between wireless nodes that are beyond normal radio range of each other by leveraging transmission capabilities of other nearby or neighboring nodes. Turning to
Turning to
These two techniques are not mutually exclusive. Depending on signal propagation and node topology, one or the other may be more effective. For example, one choice may be more energy efficient than the other. In other cases, only one of the techniques may be feasible. For example, a gap in network topology that is wider than the radio range may be crossed via cooperative diversity but not via multi-hop routing.
Accordingly, in various of the inventive embodiments, cooperative diversity and multi-hop routing can be used in combination to achieve efficient and/or extended communication across a wireless network (e.g., 100 or 200). However, integration of these two techniques may be challenging as each technique may affect the other. For example, a certain multi-hop path may affect which nodes would be useful in cooperative diversity transmission. Conversely, cooperative diversity transmission may change the set of available links from which a multi-hop path can be selected.
In a previous patent application, U.S. application Ser. No. 11/206,494 entitled “Methods and Apparatus for Providing an Integrated Multi-hop Routing and Cooperative Diversity System” filed on Aug. 17, 2005 by the present inventors, an integration of multi-hop routing and cooperative diversity was proposed which used explicit coordination between the routing and cooperation layers.
However, various embodiments of the present invention do not require such coordination thereby allowing any routing protocol that supports multiple interfaces to be integrated with any cooperation protocol that exposes multiple interfaces. To this end, various embodiments herein propose the use of virtual interfaces each representing a different pattern of potential cooperation, to integrate a multi-hop (mesh) routing layer that supports multiple communication interfaces with a cooperation-enabled MAC/PHY layer which require minimal integration between the two layers.
Mesh Routing Over Multiple Interfaces
Embodiments of the present invention may utilize a multi-hop routing protocol that supports routing across multiple MAC/PHY interfaces. By way of one non-limiting example, a wireless node might include a WLAN radio (e.g., an 802.11 radio), a WBA or WMAN radio (e.g., an 802.16 radio), and a WWAN radio (e.g. a GPRS radio). In this example, a protocol stack 300 similar to that of
Creating Multiple Interfaces With Cooperation
In various embodiments, the cooperation diversity layer or “cooperation layer” is a capability that may be integrated with the MAC and/or PHY layer of a given physical transceiver device such as a radio.
Typically a given transceiver would have a single interface provided by the software above the MAC/PHY layers. However, according to embodiments of the present invention, multiple virtual interfaces may be presented for potential use. In one example implementation, three basic types of virtual interfaces may be created by the cooperation layer: (i) a first virtual interface type in which no cooperative diversity is used; (ii) a second virtual interface type representing potential diversity transmission interfaces possible through cooperative diversity transmissions with each neighboring node individually; and (iii) a third virtual interface type representing potential diversity transmission interfaces possible with cooperative diversity transmissions utilizing a combination of neighboring nodes.
By way of example referring to
Turning to
Lastly, he third type of interface created by the cooperation layer may include interfaces created representing potential collaboration with combinations of neighboring nodes. Referring back to
Because each of the above interfaces implies cooperation with a different set of neighbors, each virtual interface created allows communication to a different set of network nodes. For example, in
It should be recognized that the “wlan” interfaces described above may simply be interfaces created for a particular WLAN MAC/PHY layer and that similar virtual interfaces might alternatively or additionally be created for other types of physical interfaces present on the wireless node such as WWPAN, WMAN and/or WWAN wireless interfaces.
Integrating the Cooperation Layer with the Multi-hop Network Layer
An example protocol stack 800 for implementing interface-based integration of cooperation and multi-hop routing is shown in
According to one or more embodiments, a cooperation component 810 is integrated with the PHY and/or MAC layers. Cooperation component 810 takes a packet received from the network layer 820 (via one of virtual interfaces VLAN0, VLAN1 or VLAN2) and transmits the packet in cooperation with the constellation of nodes represented by that virtual interface. Received packets may be delivered to an interface VLAN0, VLAN1 or VLAN2 depending on the set of nodes that cooperated to transmit the packet.
In one embodiment, MAC layer 805 may include a neighbor node list component 825 that tracks the set of nodes within communication range of the local node (without cooperation); i.e., neighbor nodes. This node list 825 may be used to determine the set of nodes the local node can cooperate with, and hence the set of available interfaces.
The multi-hop networking or routing layer 820 may be therefore be a conventional mesh routing layer since it doesn't require any explicit signaling with cooperation layer 810. In certain implementations, routing layer 820 may send and receive topology discovery messages (e.g., route updates or route requests) via the various communication interfaces. Depending on the implementation, routing layer 820 may choose to perform neighbor node discovery (typically via single hop beacons) on each of the underlying virtual interfaces to determine the set (and perhaps quality) of the available network layer links. Alternately, the cooperation layer 810 can provide an interface for assessing link quality to each effective neighbor.
Take, for example, the network of
Each node A-P may create a neighbor list that determines which interfaces will be available to the multi-hop layer (e.g., layer 820;
Note that in reality, routing table 2 may or may not include multiple entries for the same destination (they are included for clarity of explanation). In this case, cooperation with Node D (enabled using interface wlan0d) allows node A to reach node in one hop, resulting in a cost of (2) to reach node P. Cooperation with Node B (wlan0b) and no cooperation (wlan0) both result in a greater routing metric. While hop count is used as a metric in this example, other metrics (such as ETX (expected transmission count), ETT (expected transmission time), weighted cumulative ETT (WCETT), etc.) can be used to better select between different routes and different interfaces.
A packet destined for Node P (in this case originating from node A) would be forwarded to Node I, and in turn be forwarded by the multi-hop layer at Node I to the destination hop toward Node P.
Node I's routing table, complete with routes through several interfaces made available through cooperation or no cooperation may include information as shown in Table 4:
Many of these interfaces allow node P to be reached directly, allowing the packet to be delivered without further hops.
The combination of multi-hop routing and cooperative diversity can provide obvious advantages and, other than in previous U.S. application Ser. No. 11/206,494 referenced earlier has not been suggested. This application differs in several respects from the earlier application. Most notably, no explicit signaling is required between the multi-hop layer and the cooperation layer. Thus any multi-hop implementation that supports multiple communication interfaces can be used, without modification. Consequently, most of the work involved in finding and leveraging cooperators is pushed into the cooperation layer which is integrated into the MAC and/or PHY layers. The routing layer simply takes advantage of links made available by the cooperation layer.
Referring to
In one example embodiment, RF interface 1210 may be any component or combination of components adapted to send and receive modulated signals (e.g., using orthogonal frequency division multiple access (OFDMA)) although the inventive embodiments are not limited in this manner. RF interface 1210 may include, for example, a receiver 1212, a transmitter 1214 and a frequency synthesizer 1216. Interface 1210 may also include bias controls, a crystal oscillator and/or one or more antennas 1218, 1219 if desired. Furthermore, RF interface 1210 may alternatively or additionally use external voltage-controlled oscillators (VCOs), surface acoustic wave filters, intermediate frequency (IF) filters and/or radio frequency (RF) filters as desired. Various RF interface designs and their operation are known in the art and the description for configuration thereof is therefore omitted.
In some embodiments interface 1210 may be configured to provide OTA link access which is compatible with one or more of the IEEE standards or other standards for WPANs, WLANs, WMANs or WWANs, although the embodiments are not limited in this respect.
Processing portion 1250 may communicate/cooperate with RF interface 1210 to process receive/transmit signals and may include, by way of example only, an analog-to-digital converter 1252 for digitizing received signals, a digital-to-analog converter 1254 for up converting signals for carrier wave transmission, and a baseband processor 1255 for physical (PHY) link layer processing of respective receive/transmit signals. Processing portion 1250 may also include or be comprised of a processing circuit 1256 for media access control (MAC)/data link layer processing and include a neighbor node list 1257 as described previously.
In certain embodiments of the present invention, a cooperative diversity interface manager 1258 may be included in processing portion 1250 and which may function to create virtual interfaces for use by a mesh routing manager 1259 as described in any of the embodiments above. In certain embodiments, mesh routing manager 1259 include functionality to determine cost metrics and/or identify next hop nodes to build and/or store mesh routing tables using virtual interface information provided by the cooperative diversity manager 1258 similar to that described previously.
Alternatively or in addition, PHY circuit 1255 or MAC processor 1256 may share processing for certain of these functions or perform these processes independently. MAC and PHY processing may also be integrated into a single circuit if desired.
Apparatus 1200 may be, for example, a wireless base station, a client station, an access point (AP), a hybrid coordinator (HC), a wireless router and/or a network adaptor for electronic devices. Apparatus 1200 could also be a mobile subscriber station or network interface card (NIC) for an electronic computing device. Accordingly, the previously described functions and/or specific configurations of apparatus 1200 could be included or omitted as suitably desired.
Embodiments of apparatus 1200 may be implemented using single input single output (SISO) architectures However, as shown in
The components and features of apparatus 1200 may be implemented using any combination of discrete circuitry, application specific integrated circuits (ASICs), logic gates and/or single chip architectures. Further, the features of apparatus 1200 may be implemented using microcontrollers, programmable logic arrays and/or microprocessors or any combination of the foregoing where suitably appropriate (collectively or individually referred to as “logic”).
It should be appreciated that apparatus 1200 represents only one functionally descriptive example of many potential implementations. Accordingly, division omission or inclusion of block functions depicted in the accompanying figures does not infer that the hardware components, circuits, software and/or elements for implementing these functions would be necessarily be divided, omitted, or included in embodiments of the present invention.
Unless contrary to physical possibility, the inventors envision (i) the methods described herein may be performed in any sequence and/or in any combination; and (ii) the components of respective embodiments may be combined in any manner.
Although there have been described example embodiments of this novel invention, many variations and modifications are possible without departing from the scope of the invention. Accordingly the inventive embodiments are not limited by the specific disclosure above, but rather should be limited only by the scope of the appended claims and their legal equivalents.
