The invention relates to communications, and more particularly, to a system and method for communicating over a wireless network.
Wireless communications networks have found great utility in many commercial and military applications. Many wireless communications transceivers are designed for use with a single type of signal or protocol such as spread spectrum or orthogonal frequency division multiplexing (OFDM). Even if a transceiver is equipped to receive and understand more than one type of signal or protocol, the transceiver may not be able to adjust its operation or transmission parameters to optimize the performance of the transceiver.
Another factor in transceiver design is the variability of conditions in which a transceiver may be used. The transceiver may optimally respond differently in rough terrain environments than it would respond when moving rapidly. It may be difficult to maximize transmissions from the transceiver in all environments. While known multi-use transceivers provide some degree of optimization in response to differing environments, such transceivers are ill-equipped to respond to changing environments or future network configurations. Jamming and electronic counter-measure protocols are constantly changing and improving, and the complexity and demands of friendly network communications are constantly growing. Constant redesign and testing of transceivers in response to changing requirements is expensive and time-consuming.
It is therefore an object of the invention to provide a transceiver capable of maximizing its performance with a variety of signal types.
It is another object of the invention to provide a transceiver that can have its performance optimized in different operating environments.
A feature of the invention is the use of one or more state tables, loadable into the transceiver at the time of use of the transceiver, where each of the state tables provides optimal transmission parameters for the transceiver in response to observed behaviors of detected signals.
An advantage of the invention is that a transceiver can be quickly reconfigured to respond to changing environments or encountered signal types.
Another advantage of the invention is that the transceiver can be quickly and temporarily reconfigured to be optimized for specific missions or applications.
The invention provides a method of determining transmission parameters for a wireless communication transceiver. According to the method, a state table is loaded into a transceiver. The state table includes a plurality of states, each of which has a set of transmission parameters associated therewith. Signals are received from a signal source. Based upon characteristics of the received signals, the transceiver is assigned a first state. The received signals are received and processed using the set of transmission parameters associated with the first state. A behavior of the received signals is observed. It is determined whether the behavior exceeds a threshold associated with the first one of the plurality of states. The transceiver is assigned a second state when the behavior exceeds the threshold. The received signals are received and processed using the set of transmission parameters associated with the second state. The assigning of the second state operates to change at least one of signal transmission rate and transmission power used with the received signals.
The invention also provides a wireless transceiver including transceiver circuitry configured to receive and send wireless signals according to a plurality of transmission parameters. A memory is configured to receive a state table. The state table includes a plurality of states. Each state contains values for each of the plurality of transmission parameters. A processor observes at least one behavior of an incoming signal and assigns one of the plurality of states, with the respective values for each of the plurality of transmission parameter, to the transceiver circuitry, wherein the assigned state optimizes performance of the transceiver given the observed behavior.
The invention further provides a wireless transceiver including: means for loading a state table into a transceiver that includes a plurality of states, each of the plurality of states having a set of transmission parameters associated therewith; means for receiving signals from a signal source; based upon characteristics of the received signals, means for assigning to the transceiver a first state; means for receiving and processing the received signals using the set of transmission parameters associated with the first state; means for observing a behavior of the received signals; means for determining whether the behavior exceeds a first threshold associated with the first state; means for assigning to the transceiver a second state when the behavior exceeds the threshold; and means for receiving and processing the received signals using the set of transmission parameters associated with the second state, wherein the assigning of the second state operates to change at least one of signal transmission rate and transmission power used with the received signals.
A technique is described here to generalize the configuration of transmission parameters and the algorithm used to adapt them at runtime. The goal is to make the transceiver as unaware as possible of the specific properties of each received signal. This will minimize the changes required as development proceeds and the radios are tested in the field. When it is desirable to change the way the transceiver behaves in response to specific channel conditions, it will just be a matter of generating a new configuration and reloading the transceivers(s). To accomplish this the software will avoid hard coded parameters and instead rely on configuration data to provide it with the database needed to control the received signal.
Software portion 18 of the state machine includes discrete sets of operating parameters for the transceiver. Each discrete set can be considered a state, which as shown at reference number 6 in
To move from one state to another, it must be determined whether the parameters associated with a state are appropriate for the signal given the behavior of the signal. To make this determination, state machine 14 observes signal behavior using at least two measurements: the signal-to-noise ratio (SNR) of the observed incoming signal, and the symbol error rate (SER) of the observed incoming signal. An unacceptably high SNR indicates that the transceiver should use a state with higher transmit power level than the currently used state. A very high SNR indicates that the transceiver may move to a state with a lower transmit power level than the currently used state, without unduly affecting transmission quality. An unacceptably high SER indicates that the transceiver should use a state with a lower data transmission rate than what is provided by the currently used state. A very low SER indicates that the transceiver may use a state with a higher data transmission rate than what is provided by the currently used state.
Determining whether the SER and the SNR of a given signal are unacceptable at a current state is preferably accomplished using a combination of thresholds 34, 36, 38 and 40. Exceeding any one of these threshold levels will cause the state machine to instruct the transceiver circuitry to use parameters associated with a different state. As depicted in
The threshold values used to determine whether to move to a different state may be standard throughout the state table (10e-5 for SER, for example), or each state may have unique threshold values.
If the transceiver is operating in a state on an edge of the state table, for example state 9, it may not be possible to move to another state that further reduces power. In such an instance it may be preferable to increase the rate instead, for example moving to state 13. Likewise, in the case of state 3, it may not be possible to move to another state that further reduces the data transmission rate. In such an instance it may be preferable to increase the power level instead, for example moving from state 3 to state 2.
The states in
The thresholds of adjacent states are selected so that slight changes in the observed behaviors (e.g., SER and SNR) immediately after a state change do not result in an immediate return, or toggle, to a previous state.
The decision of whether to change from one state to another may take into account the relative stability of the observed behaviors. For example, a relatively constant value for the SNR or SER may suggest future stability of those values, and it would be considered proper to change states based upon a comparison of the observed behaviors to the corresponding thresholds. On the other hand, a wildly oscillating SER value may suggest uncertainty as to future stability of that measurement, and such uncertainty should be taken into account when deciding whether to change states. According to the invention, a time sample is taken of the observed behaviors, and a mean deviation of the sample is calculated. The mean deviation is multiplied by a weighting factor, which may be different for each threshold and each state, and the combined value is used when comparing the observed behaviors with the respective thresholds. For example, as shown in
SER+NσSER<StateTHRESH−34
where
SER is the observed symbol error rate,
N is the weighting factor,
σSER is the mean deviation of the SER, and
StateTHRESH−34 is a value associated with threshold 34.
The transceiver will change to a state having a decreased transmission rate when the following expression is true:
SER+NσSER>StateTHRESH−36
where StateTHRESH−36 is a value associated with threshold 36.
The transceiver will change to a state having a reduced power level when the following expression is true:
SNR−NσSNR>StateTHRESH−38
where
SNR is the observed signal-to-noise ratio,
N is the weighting factor,
σSNR is the mean deviation of the SNR, and
StateTHRESH−38 is a value associated with threshold 38.
The transceiver will change to a state having an increased power level when the following expression is true:
SNR−NσSNR<StateTHRESH−40
where StateTHRESH−40 is a value associated with threshold 40.
The effect of considering a weighted mean deviation of the observed behavior is to not change to a different state if there is sufficient instability in the observed behavior. This prevents premature or unnecessary state changes.
For effective network communications, each transceiver in a network may have loaded therein a state table for each type of signal it is anticipated to encounter, such as OFDM, spread spectrum protocols, or the like. Unknown or unanticipated signal types may be assigned a default state table. Furthermore, each node may also have a state table for multiple scenarios in which each type of signal may be encountered. Scenarios may include rough terrain, non-moving or slow-moving nodes, high movement nodes (such as fixed-wing aircraft), hostile signal environment (i.e., jamming & surveillance).
The transceiver may access state tables having different strategies used in transmitting and receiving signals. For instance, if it is desirable for the transceiver to maximize its data transmitting rate, the transceiver is loaded with a ‘maximize rate’ state table reflecting that strategy. The transceiver moves through states in the ‘maximize rate’ state table such that transmit power is increased until a maximum data transmitting rate is achieved. On the other hand, it may be desirable to maximize the reuse, or simultaneous use, of communication resources, and the transceiver would then be loaded with a ‘maximize reuse’ state table reflecting that strategy. The transceiver maintains a list of neighboring transceivers with which it desires to communicate. The transceiver moves through entries in the state table such that transmit power is increased until the transceiver is communicating with the desired neighboring transceivers. At that point the transceiver moves through states in the state table that maintain the level of transmit power but optimize other transmission parameters as shown in
Alternatively, it may be preferable to use a single state table that may be used regardless of the type of transmission scenario encountered.
1. A weak signal, evidenced by low signal strength, low SNR, and high SER. A weak signal may be advantageously benefited by increasing power at the expense of the data rate, and a transceiver operating in high traffic in such a scenario would therefore follow line 60 from a low-power, high-rate state 56 to a high-power, low-rate state 58, provided the thresholds for each intermediate state are met (
2. A multipath scenario, evidenced by high SNR, high signal strength, and high SER. A transceiver operating in high or low traffic in such a scenario would likely follow line 64 from low-power, high data-rate state 56 to a low-power, low-data rate state 59, provided the appropriate thresholds for each intermediate state are met.
3. A high-interference scenario, evidenced by low SNR, high SER, and high received signal strength. A transceiver encountering interference would likely be benefited by increasing power at the expense of the data rate to provide a more robust transmission, and the transceiver when operating in high traffic in such a scenario would likely follow line 66 from low-power, high data-rate state 56 to high-power, low data-rate state 58, provided the appropriate thresholds for each intermediate state are met. A transceiver operating in low traffic in a high-interference scenario would likely follow line 68 between states 56 and 58. Line 68 follows a path that boosts power more quickly than the path followed by line 66, and in low traffic situations a transceiver is more able to do so.
4. A scenario in which it is determined that a good link has been established, as evidenced by a low SER. A transceiver having a good link could increase data rate at the expense of power to provide the most efficient transmission, and the transceiver when operating in high traffic in this scenario would likely follow line 70 between high-power, low data-rate state 58 to low-power, high data-rate state 56, provided the appropriate thresholds for each intermediate state are met. A transceiver operating in low traffic in a good-link scenario would likely follow line 72 between states 58 and 56. Line 72 follows a path that increases the data rate more quickly than the path followed by line 70, and in low traffic situations a transceiver is more able to do so.
The transmission parameters of a state table can be used to produce a preference index that assists a transceiver in determining which of several communication links to use when sending a transmission. In
The disclosure has described the nature of the state table and the contents of its component states. A method of using the state table, according to the invention, and as shown at reference number 80 in
In step 88 state machine 14 monitors or observes the received signal, and derives values representative of behaviors of the signal. As previously explained, such behaviors may include the SNR and the SER of the received signal. State machine also determines the mean deviation, over time, of the SNR and SER. In step 90 it is determined whether either the observed values of the SNR or the SER are beyond thresholds associated with the assigned state. If so, in step 92 transceiver 10 is directed to use a different state as previously described, and neighboring transceivers are notified of the change in state.
This document has presented a technique for making a very complex transmission parameter algorithm table driven so that it can be configured offline. The loading of a desired state table is performed after the transceiver circuitry has been finalized, and such loading may be performed even in real time during a specific mission in response to changes in environment, signal type, or signal strategy as described herein. An advantage of the invention is that the behavior of the transceiver and all of the characteristics of the received signal can be specified at run time, thereby giving the maximum flexibility during the development and fielding of a radio type. Without modifying the software or the transceiver circuitry it will be possible to change the way the radio responds to various channel conditions and adapts to the different types of signals it must support.
Another advantage of the invention is that because the state table is loaded into the transceiver rather than hard-wired, portions of the transceiver may be designated as unclassified because classified algorithm and performance details will be loaded rather than hard-coded.
Still another advantage of the invention is that the multiple transmission scenarios can be accommodated in either a single state table or in multiple state tables.
While the invention has been disclosed in its preferred form, the specific embodiments thereof as disclosed and illustrated herein are not to be considered in a limiting sense as numerous variations are possible. The subject matter of the invention includes all novel and non-obvious combinations and subcombinations of the various elements, features, functions and/or properties disclosed herein. No single feature, function, element or property of the disclosed embodiments is essential to all of the disclosed inventions. Similarly, where the claims recite “a” or “a first” element or the equivalent thereof, such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements.
It is believed that the following claims particularly point out certain combinations and subcombinations that are directed to the disclosed inventions and are novel and non-obvious. Inventions embodied in other combinations and subcombinations of features, functions, elements and/or properties may be claimed through amendment of the present claims or presentation of new claims in this or a related application. Such amended or new claims, whether they are directed to a different invention or directed to the same invention, whether different, broader, narrower or equal in scope to the original claims, are also regarded as included within the subject matter of the invention of the present disclosure.
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