COST EFFICIENT SPECTRAL-REUSE TRANSCEIVER
An operational mechanism enables frequency re-use techniques, including selective frequency hopping and channel aggregation, on very low-cost transceiver hardware.
The present application is a continuation of, and claims the benefit of U.S. patent application, Ser. No. 12/172,124, filed Jul. 11, 2008, (the '124 application). The '124 application is a continuation-in-part of and claims the benefit of U.S. patent application Ser. No.: 10/730,753, issued as U.S. Pat. No. 7,457,295 on Nov. 25, 2008, filed Dec. 8, 2003, (the '753 application), and incorporates by reference and claims priority to U.S. patent application, Ser. No. 60/432,223, filed Dec. 10, 2002, (the '223 application). The '124 application further incorporates and claims the benefit of U.S. patent application, Ser. No. 11/532,306, filed Sep. 15, 2006 (the '306 application), which incorporates by reference and claims priority to U.S. patent application Ser. No. 60/784,105, filed Mar. 20, 2006, (the '105 application). The disclosures of each of the five cited applications are hereby incorporated by reference.
FIELD OF THE INVENTIONThe present invention relates in general to communication systems and subsystems thereof, and is particularly directed to a ‘cost-efficient’ embodiment that may be employed by the communications controller of a spectral reuse transceiver of a communication system of the type disclosed in the above-identified '753 application, to enable spectral-reuse methods in transceivers having many of the benefits of the communication system disclosed in the above identified '753 and '306 applications, having minimal processor and memory capability.
BACKGROUND OF THE INVENTIONAs described in the above-identified '753 application, in some radio bands, such as the 217-220 MHz VHF band, as a non-limiting example, governmental licensing agencies (e.g., the Federal Communications Commission (FCC)) customarily grant primary licensees non-exclusive use of the band for a variety of communication services, such as push-to-talk voice transmission. These primary users pay for this licensed use with an expectation that they will not encounter interference by other users. The FCC also allows secondary users to access the same band and the same channels within the band on a ‘non-interfering’ or secondary basis, whereby a channel may be used by a secondary, non-licensed, user, so long as the primary user is not using that channel.
The FCC and similar agencies in foreign countries are continually looking for ways that allow expanded use of these licensed radio frequency bands, without reducing the quality of service available to the primary users. For secondary users, these bands provide a cost-free opportunity with excellent radio transmission properties for telemetry and other applications. Because secondary users must not interfere with primary users, complaints of interference from a primary user to the FCC may result in its issuing an administrative order requiring that the secondary user move to another portion of the band or leave the band entirely. Such a spectral transition is disruptive to the secondary user's service and can be expensive, especially if site visits, equipment modification, or exchange are required, in order to implement the mandated change. It will be appreciated, therefore, that there has been a need for a mechanism that allows a secondary user to employ a licensed band on a non-interfering basis and will adapt the radio's frequency usage should new primary users appear. It should be noted that primary users always have priority over secondary users, there is no first-use channel frequency right for secondary users.
Advantageously, the invention described in the above-referenced '753 application successfully addresses this need by means of a monitored spectral activity-based link utilization control mechanism. Briefly reviewing this link utilization control mechanism, which may, without limitation, be used in a star-configured communication system, such as that depicted in the reduced complexity diagram of
For this purpose, the master site 10 periodically initiates a clear sub-channel assessment routine, in which the master site and each of the remote sites 12 participate, in order to compile or ‘harvest’ a list of non-interfering or ‘clear’ sub-channels (such as 6.25 kHz wide sub-channels), which may be used by participants of the network for conducting communication sessions that do not ostensibly interfere with any licensed user. By transmitting on only (clear) sub-channels, a respective site's spectral reuse transceiver is ensured that it will not interfere with any primary user of the band of interest.
Except when it is transmitting a message to the master site, each remote user site sequentially steps through and monitors a current list of clear sub-channels (that it has previously obtained from the master site), in accordance with a pseudo-random (PN) hopping sequence that is known a priori by all the users of the network, looking for a message that may be transmitted to it by the master site transceiver. During the preamble period of any message transmitted by the master site, each remote site's transceiver scans all frequency bins within a given spectrum for the presence of energy. Any bin containing energy above a prescribed threshold is marked as a non-clear sub-channel, while the remaining sub-channels are identified as clear and therefore available for reuse sub-channels.
Whenever a remote site notices a change in its clear sub-channel assessment, it reports this to the master site at the first opportunity. As the master site has received clear sub-channel lists from all the remote sites, it logically combines all of the clear sub-channel lists, to produce a composite clear sub-channel list. This composite clear sub-channel list is stored in the master site's transceiver and is broadcast to all of the remote sites over a prescribed one of the clear sub-channels that is selected in accordance with a PN sequence through which clear sub-channels are selectively used among the users of the network. When the composite clear sub-channel list is received at a respective remote site it is stored in its transceiver.
To ensure that all communications among the users of the network are properly synchronized (in terms of the composite clear sub-channel list and the order through which the units traverse, or ‘hop’ through, the clear sub-channel entries of the clear sub-channel list), the master site's transceiver transmits an initialization message on an a priori established clear sub-channel, which each of the remote units monitors. This initialization message contains the clear sub-channel list, an identification of the preamble channel, a PN sequence tap list, and a PN seed that defines the initial sub-channel and hopping sequence for the duration of an upcoming transmit burst. Once a remote site has received an initialization message, that site will transition to normal multiple access mode.
For further details of the architecture and operation of the spectral reuse link control mechanism disclosed in the above-referenced '753 and '306 applications, attention may be directed to those documents. They will not be detailed here, in order to focus the present description on the problem of a ‘cost efficient’ embodiment, whereby lower-end processors, smaller memory devices, and lower system requirements may be used, thereby lowering the cost of manufacture and deployment of a spectral reuse communication system, while preserving many of the benefits of spectral reuse.
SUMMARY OF THE INVENTIONIn accordance with the present invention, this ‘cost efficient’ goal is successfully addressed by prescribing a set of operating parameters described in the '753 and '306 applications, including the number of carriers simultaneously transmitted (‘multi-carriers’), the sub-channel size (typically in kHz), hopping rate (every ‘n’ symbols, for example), the hopping pattern, the interference threshold by which the transceiver decides to hop to a new frequency set, and the clear sub-channel assessment period or trigger.
A first of these parameter sets lowers the microprocessing and memory required of the transceiver, so that lower-cost components can be used. A second of these parameter sets further lowers the microprocessing and memory required of the transceiver and improves the clear sub-channel assessment.
In another embodiment of the present invention, a parameter set will be chosen so that the transceiver will ‘aggregate’ and therefore provide greater re-use of said licensed channels. This embodiment uses the example of occasional-use voice channels by which the present embodiment provides data service during periods of non-voice usage.
In another embodiment of the present invention, the transceiver provides increased upstream bandwidth through the use of a plurality of receiver circuits.
Before describing the details of the ‘cost efficient’ spectrum reuse transceiver of the present invention, it should be observed that the invention essentially involves special cases of the sub-channel hopping control mechanism executed by the communications control processor of the spectral reuse transceiver of the type disclosed in the above-referenced '753 application, that involves the execution of one or more prescribed discriminators or sub-channel selection filters, so as to effectively reduce the receiving end of a transceiver link. As will be described, these filter functions are readily implemented by appropriately setting the configuration parameters used by the communications controller of the transceiver disclosed in the '753 application to control the operation of the transceiver. The architecture of the transceiver of the '753 application remains unchanged, except as noted. As a consequence, the present invention has been illustrated in the drawings by readily understandable diagrammatic illustrations, which include a generalized network architecture diagram, and a sub-channel sub-division diagram, that show only those details that are pertinent to the invention, so as not to obscure the disclosure with details which will be readily apparent to one skilled in the art having the benefit of the description herein.
As pointed out briefly above, an essential objective of the invention is to effectively cost-reduce the transceiver selection of transceiver parameters. Non-limiting, but preferred examples of such parameters include: 1—limiting number of carriers that the transceiver can simultaneously transmit; and 2—limiting the rate of sub-channel hopping. The operation and effect of each of these and other parameters will be discussed individually below.
To facilitate an understanding of the functionality and effect of the first discriminator—division of available channels—attention may be directed to
For purposes of reducing the hardware costs of the transceiver of the present invention, some or all of the operating parameters described above may be set advantageously. For example, the number of simultaneously transmitted hopping channels 22 may be reduced to a few or to one hopping sub-channel 22a-z, and the hopping sequence may be restricted to an administratively determined fixed set of hopping channels 22a-z, and the dwell time for transmitting on the same sub-channel may be unlimited until, as will be shown below in the description of additional figures, when the presently used hopping sequence 22a-z is interfered with, in which case another hopping sub-channel in the set of hopping channels 22a-z will be selected. By making these advantageous selections of the operating parameters of the present invention, the processing power and memory requirements for the transceiver's one or more control processors may be significantly reduced, thereby reducing cost and reducing energy requirements.
Refer now to
Graph 35 of
Graph 38 of
In another embodiment of the present invention, the transceiver (not shown) in graph 38 of
A sub-channel assessment and selection mechanism, shown in the flowchart of
Once assessment period 406 is complete, the base station transceiver has a candidate new hopping sequence if a new interference pattern had emerged. In the preferred embodiment of the present invention, the candidate hopping sequence is further filtered by interference reports reported to the base station transceiver from a remote transceiver (or the far end of a point-to-point connection, for example), as indicated by the merge interference 408 step of
A sub-channel assessment and selection mechanism, shown in the flowchart of
Once assessment period 446 is complete, the remote transceiver begins merge interference step 448. In step 448, if there is new interference or new absence of interference on any hopping sub-channels, the remote transceiver will merge the assessment data of step 446 with the present system-wide hopping sub-channel interference previously provided by the base station transceiver, wherein the merged data will include an indication of newly detected interference and newly detected lack of interference. In decision block 450, the remote transceiver will return to step 444 via path 452 if said merged data indicates that no newly detected interference and no newly detected lack of interference was found in step 448; otherwise, step 456 begins. In step 456, the remote transceiver sends the merged data to the base station transceiver, for example, in a maintenance message which may, without limitation, be sent asynchronously, periodically, or when polled by the base station transceiver. The remote transceiver then returns to begin a new sample spectrum period 444.
In another embodiment of the present invention, during assessment period 406 of
In another embodiment of the present invention, during the new clear sub-channel map period 416 of
In another embodiment of the present invention, during new clear sub-channel map period 416 of
In another embodiment of the present invention, during new clear sub-channel map period 416 of
In another embodiment of the present invention, during sample spectrum period 404 of
In another embodiment of the present invention, the base station transceiver is a full-duplex radio and selects a pair of interference-free channels rather than a single sub-channel (for half-duplex communications.) In another embodiment of the present invention, the media access protocol is not poll-response, but is aloha, slotted-aloha, TDD, TDMA, or another media access protocol well-known to one skilled in the art.
A sub-channel assessment and selection mechanism, shown in the flowchart of
In another embodiment of the present invention, during assessment period 52, the base station and each of the remote stations detect interference in each hopping sub-channel by measuring the signal strength, typically the RSSI value for each of said hopping channels; during the assessment reporting period, the said RSSI value for each of said hopping channels is included in the assessment report. In the subsequent new sub-channel select period 59, the base station uses the RSSI value and a threshold parameter therefor to determine if a hopping sub-channel has an interfering signal.
In another embodiment of the present invention, during the new channel select period 59, the base station selects a new hopping sub-channel by choosing a hopping sub-channel with the lowest RSSI value.
In another embodiment of the present invention, during the new channel select period 59, the base station selects a new hopping sub-channel by choosing a hopping sub-channel with the lowest RSSI value below a threshold parameter therefor. If there is no hopping sub-channel with a said lowest RSSI value below a said threshold parameter, then, according to a policy configured in the transceiver software, the transceiver may select a hopping sub-channel with a said lowest RSSI value, or cease transmitting until an interference-free hopping sub-channel becomes available, or lower its transmit power, or lower its throughput rate, or a combination thereof, or similar policies well-known to one skilled in the art.
In another embodiment of the present invention, the base station transceiver is a full-duplex radio and selects a pair of interference-free channels rather than a single sub-channel (for half-duplex communications.) In another embodiment of the present invention, the media access protocol is not poll-response, but is aloha, slotted-aloha, TDD, TDMA, or another media access protocol well-known to one skilled in the art.
Referring now to
According to one embodiment of the present invention, transceiver 60 uses transmitter 61 and one of the receivers 62-63, for user traffic, and uses the other of the receivers 62-63 for scanning hopping channels for interference. This arrangement allows transceiver 60 to scan for interference on the hopping channels even while receiving or transmitting on the operational hopping sub-channel. In one embodiment of the present invention, transceiver 60 scans all hopping channels except the operational hopping sub-channel at any or all times during the periods 51-59 of
In another embodiment of the present invention, transceiver 60 of
In another embodiment of the present invention, transceiver 60 of
Refer now to
Referring now to
Mobile transceiver 808 Rem-1 has two receivers, as described in the descriptions of
While we have shown and described several embodiments in accordance with the present invention, it is to be understood that the same is not limited thereto but is susceptible to numerous changes and modifications as known to a person skilled in the art. There is no intention that the application be limited to the details shown and described herein, but it is intended that the application cover all such changes and modifications as are obvious to one of ordinary skill in the art. For example, the transceivers described in the above-identified '753 application may operate in a star network. There is no intention to limit either the '753 application or the instant application to such a configuration and, without limitation, radio links between transceivers in other topologies, such as point-to-point, and individual links in mesh networks, as examples, can employ the cost-reduction and other improvements of the present invention as well.
Claims
1. On a frequency hopping spectral reuse transceiver communicating over sub-channels of a prescribed communication bandwidth, a method of reducing the hardware requirements of the transceiver comprising the step of selecting one or more operational parameters of the transceiver's spectrum detection and frequency hopping capabilities so as to minimize for the transceiver's control processor's memory requirements or microprocessing requirements or both.
2. The method of claim 1 wherein said one or more operational parameters are selected from the group comprised of the number of sub-channels simultaneously transmitted, the sub-channel size, the frequency hopping rate, the hopping pattern, the interference threshold at which the transceiver hops to a new frequency, the clear sub-channel assessment period, and the trigger for the sub-channel assessment period.
3. On a network of frequency hopping spectral reuse transceivers, a method for creating a new frequency hopping sequence over which communications may be conducted by selecting sub-channels for communication comprising the steps of:
- a. a base station transceiver analyzing the spectrum of potential sub-channels over which communications may be conducted wherein said analysis comprises the measurement of signal levels on said sub-channels to determine their suitability for conducting communications by detecting the presence and absence of interfering signals and the recordation of said measurements;
- b. said base station transceiver compiling a sample spectrum of suitable potential sub-channels identified in step a;
- c. said base station transceiver analyzing which sub-channels of the frequency hopping sequence currently in use have new interference;
- d. said base station transceiver determining which sub-channels not currently in the frequency hopping sequence are interference free;
- e. said base station transceiver constructing a new frequency hopping sequence by adding the sub-channels compiled in step b to those sub-channels in the current frequency hopping sequence that are interference free and subtracting those sub-channels identified in step c.
4. The method of claim 3 comprising the further steps of:
- i. a remote transceiver analyzing the spectrum of potential sub-channels over which communications may be conducted;
- ii. said remote transceiver compiling an interference identifying on which sub-channels the remote transceiver has detected interference;
- iii. said remote transceiver sending said interference report to the base transceiver;
- iv. said base station transceiver further filtering its new frequency hopping sequence by subtracting those sub-channels identified in said interference report.
5. The method of claim 4 wherein said spectrum analysis comprises the measurement of the received signal strength indicator for each potential sub-channel to determine whether said sub-channel is suitable for conducting communications.
6. The method of claim 5 wherein said base station transceiver compares the received signal strength indicators for each sub-channel to a selected threshold value for determining whether said sub-channel is suitable for conducting communications.
7. The method of claim 5 wherein said base station transceiver selects a new hopping sub-channel for conducting communications by selecting the candidate sub-channel with the lowest received signal strength indicator value.
8. The method of claim 6 wherein said base station transceiver selects a new hopping sub-channel with the lowest received strength indicator value below a selected threshold value.
9. The method of claim 4 wherein said base station transceiver excludes selection of a hopping sub-channel adjacent to the sub-channel currently in use when said base station transceiver constructs a new frequency hopping sequence.
10. The method of claim 4 wherein said base station transceiver excludes selection of a hopping sub-channel adjacent to the sub-channel currently in use when said base station transceiver and said remote transceiver are engaged in spectrum analysis.
11. The method of claim 4 wherein said base station transceiver is a full-duplex radio and wherein said base station transceiver selects a pair of sub-channels from the frequency hopping sequence over which to conduct communications.
12. The method of claim 3 wherein at least one of said receivers is used to conduct spectrum analysis on a network of frequency hopping spectral reuse transceivers and further wherein said base station transceiver comprises at least one transmitter and two or more receivers.
13. The method of claim 12 wherein more than one receiver is used to conduct spectrum analysis.
14. The method of claim 3 wherein the spectrum analyzed includes authorized licensed channels, further comprising the step that said base transceiver deems licensed channels over which the transceiver detects communications as interfering channels in compiling the frequency hopping spectrum.
15. On a network of frequency hopping spectral reuse transceivers, wherein said network comprises more than one base station transceiver and wherein a mobile transceiver comprises at least two receivers, a method for determining hand-off procedures between base station transceivers comprising the steps:
- a) monitoring signal strength levels from the presently associated base station transceiver using one receiver;
- b) simultaneously measuring signal strength levels from other base station transceivers within network range using a different receiver; and
- c) comparing the respective signal strengths to determine whether the mobile transceiver should disassociate from one base station transceiver to another base station transceiver.
Type: Application
Filed: Dec 23, 2010
Publication Date: Apr 21, 2011
Inventor: Bryan Kattwinkel (Palm Bay, FL)
Application Number: 12/977,951
International Classification: H04B 1/7143 (20110101); H04L 5/14 (20060101);