Description:TECHNICAL FIELD
The present disclosure relates generally to the field of communication network. More particularly, the present disclosure relates to a multi-user downlink non-orthogonal multiple access (NOMA) communication system and a method thereof.
BACKGROUND
Internet of Things (IoT) connects billions of devices to the network resulting in an exponential surge in the number of connected devices. However, the diverse IoT-enabled applications demand massive connectivity, low latency and extensive coverage. Hence, futuristic wireless communication system designs are required to meet the demand of IoT-enabled applications. Non orthogonal multiple access (NOMA) is considered a potential multiple access technique that can address the challenges of high connectivity for massive IoT devices. In NOMA, due to multiple users sharing the same resource block, the desired user suffers from multi-user interference. Thus, multi-user detection at the receiver is needed to mitigate the multi user interference. Successive interference cancellation (SIC) is the most prevalent algorithm for canceling the interference in the NOMA. Since SIC is a layered algorithm, it suffers from error propagation at each layer due to the wrong decisions in the earlier detection layer. In practical systems, error propagation is inevitable, and thus SIC is generally imperfect. To overcome the drawback of SIC receiver, we propose a multiple-feedback based SIC (MF-SIC) algorithm for downlink NOMA system.
One of the key steps to bring NOMA into standardization involves prototype development and conducting real-world testing to validate NOMA’s performance. The performance analysis of MF SIC based NOMA for multi-user NOMA systems is proposed that provides a reliable error performance. The proposed algorithm outperforms the conventional SIC. Performance of the NOMA system with the SIC algorithm is extensively analyzed in the literature, which mainly focuses on outage probability, sum-rate and error rate. The SIC is considered a detector module used in the receivers in a NOMA system. The SIC detects the user signals from the strongest to the weakest in succession. The interference coming from the weaker users is unavoidable, even if all the stronger user signals are perfectly removed. The interference results in inevitable decoding errors, leading to imperfect SIC. Thus, the significant interference in SIC detection results in an error floor. Therefore, the imperfect SIC has a significant impact on the performance of NOMA, particularly in massive access systems.
Therefore, there exists a need for an improved technique that can solve the aforementioned problems of conventional interference cancellation techniques.
SUMMARY
In view of the foregoing, a multi-user downlink NOMA communication system is disclosed. The NOMA communication system includes a base station, a plurality of users, and a receiver. The plurality of users are served by the base station transmitting signals over a shared downlink channel. The receiver associated with each user of the plurality of users, and configured to estimate a decoded symbol point corresponding to received data. The receiver is further configured to determine a distance between the decoded symbol point and a received symbol point. The receiver is further configured to initialize a set of neighboring constellation points when the distance is greater than a predefined threshold. The receiver is further configured to select an optimal decoded symbol point from the set of neighboring constellation points. The receiver is further configured to reiterate determination of the distance, initialization of the set of neighboring constellation points, and selection of the optimal decoded symbol point until the distance is less than the predefined threshold. In each reiteration, the decoded symbol point is replaced by the optimal decoded symbol point.
In some embodiments of the present disclosure, the set of neighboring constellation points has a predefined size that depends on a modulation technique employed by the base station.
In some embodiments of the present disclosure, the modulation technique employed by the base station for the downlink transmission is Quadrature Amplitude Modulation (QAM) technique.
In some embodiments of the present disclosure, when the distance is less or equal to the predefined threshold, the receiver is configured to multiply a power allocation coefficient to the received data when a signal from a target user is not detected such that the power allocation coefficient facilitates detection of the signal from the target user.
In some embodiments of the present disclosure, when the distance is less or equal to the predefined threshold, the receiver is configured to label the estimated decoded symbol point as the optimal decoded symbol point when a signal from a target user is detected.
In some embodiments of the present disclosure, the receiver is configured to formulate a decision metric for each possible symbol intended for the target user based on the determined distances.
In some embodiments of the present disclosure, the decision metric incorporates factors selected from one of, the distances to neighboring constellation points, the signal-to-interference-plus-noise ratio (SINR), and other channel conditions.
In some embodiments of the present disclosure, the receiver is further configured to employ a reliable region concept that requires a reliable region such that the reliable region concept facilitates detection of the decoded symbol point and iterative interference cancellation. The reliable region represents an area within a signal space where the received symbol point is reliably detected and decoded.
In some embodiments of the present disclosure, the receiver is further configured to employ a predefined stopping criterion to facilitate the iterative interference cancellation, wherein the predefined stopping criterion is based on one of, (i) quality of the signals and (ii) maximum number of iterations.
In some embodiments of the present disclosure, the receiver is configured to select the optimal decoded symbol point by way of the decision metric. To select the optimal decoded symbol point, the receiver is configured to determine a probability of correctness of the decoded symbol.
In an aspect of the present disclosure, a method for selecting an optimal decoded symbol point in a multi-user downlink NOMA communication network is disclosed. The method includes a step of transmitting, by way of a plurality of users served by a base station, signals over a shared downlink channel. The method further includes a step of estimating, by way of a receiver associated with each user of the plurality of users, a decoded symbol point corresponding to received data. The method further includes a step of determining, by way of the receiver, a distance between the decoded symbol point and the received symbol point. The method further includes a step of initializing, by way of the receiver, a set of neighboring constellation points when the distance is greater than a predefined threshold. The method further includes a step of selecting, by way of the receiver, the optimal decoded symbol point from the set of neighboring constellation points. The method further includes a step of reiterating determining the distance, initializing the set of neighboring constellation points, and selecting the optimal decoded symbol point until the distance is less than the predefined threshold. In each reiteration, the decoded symbol point is replaced by the optimal decoded symbol point.
BRIEF DESCRIPTION OF DRAWINGS
The above and still further features and advantages of aspects of the present disclosure becomes apparent upon consideration of the following detailed description of aspects thereof, especially when taken in conjunction with the accompanying drawings, and wherein:
FIG. 1 illustrates a block diagram of a multi-user downlink non-orthogonal multiple access (NOMA) communication system, in accordance with an embodiment of the present disclosure;
FIG. 2 illustrates a block diagram of the processing circuitry, in accordance with an embodiment of the present disclosure; and
FIG. 3 illustrates a flowchart of a method for selecting an optimal decoded symbol point in a multi-user downlink NOMA communication network, in accordance with an embodiment of the present disclosure.
To facilitate understanding, like reference numerals have been used, where possible, to designate like elements common to the figures.
DETAILED DESCRIPTION
Various aspects of the present disclosure provide a multi-user downlink non-orthogonal multiple access (NOMA) communication system and a method thereof. The following description provides specific details of certain aspects of the disclosure illustrated in the drawings to provide a thorough understanding of those aspects. It should be recognized, however, that the present disclosure can be reflected in additional aspects and the disclosure may be practiced without some of the details in the following description.
The various aspects including the example aspects are now described more fully with reference to the accompanying drawings, in which the various aspects of the disclosure are shown. The disclosure may, however, be embodied in different forms and should not be construed as limited to the aspects set forth herein. Rather, these aspects are provided so that this disclosure is thorough and complete, and fully conveys the scope of the disclosure to those skilled in the art. In the drawings, the sizes of components may be exaggerated for clarity.
It is understood that when an element or layer is referred to as being “on,” “connected to,” or “coupled to” another element or layer, it can be directly on, connected to, or coupled to the other element or layer or intervening elements or layers that may be present. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
The subject matter of example aspects, as disclosed herein, is described specifically to meet statutory requirements. However, the description itself is not intended to limit the scope of this disclosure. Rather, the inventor/inventors have contemplated that the claimed subject matter might also be embodied in other ways, to include different features or combinations of features similar to the ones described in this document, in conjunction with other technologies. Generally, the various aspects including the example aspects relate to a multi-user downlink non-orthogonal multiple access (NOMA) communication system and a method thereof.
FIG. 1 illustrates a block diagram of a multi-user downlink non-orthogonal multiple access (NOMA) communication system 100, in accordance with an embodiment of the present disclosure. The system 100 may include a base station 102, a plurality of users 104a-104n (hereinafter collectively referred to and designated as “the users 104”) and a receiver 106 that may be associated with each user of the users 104.
The base station 102 may be configured to serve the users 104. The base station 102 may be configured to transmit signals. Specifically, the base station 102 may be configured to transmit the signals over a shared downlink channel 108.
The shared downlink channel 108 may be configured to enable the base station 102 to transmit the signals to the users 104. Examples of the shared downlink channel 108 may include, but not limited to, a modem, a network interface such as an Ethernet card, a communication port, and/or a Personal Computer Memory Card International Association (PCMCIA) slot and card, an antenna, a radio frequency (RF) transceiver, one or more amplifiers, a tuner, one or more oscillators, a digital signal processor, a coder-decoder (CODEC) chipset, a subscriber identity module (SIM) card, and a local buffer circuit. It will be apparent to a person of ordinary skill in the art that the shared downlink channel 108 may include any device and/or apparatus capable of providing wireless or wired communications between the base station 102 and the users 104.
The shared downlink channel 108 may include suitable logic, circuitry, and interfaces that may be configured to provide a number of network ports and a number of communication channels for transmission and reception of data related to operations of various entities (such as the base station 102 and the users 104) of the system 100. Each network port may correspond to a virtual address (or a physical machine address) for transmission and reception of the communication data. For example, the virtual address may be an Internet Protocol Version 4 (IPV4) (or an IPV6 address) and the physical address may be a Media Access Control (MAC) address. The shared downlink channel 108 may be associated with an application layer for implementation of communication protocols based on one or more communication requests from the base station 102 and the users 104. The communication data may be transmitted or received, via the communication protocols. Examples of the communication protocols may include, but not limited to, Hypertext Transfer Protocol (HTTP), File Transfer Protocol (FTP), Simple Mail Transfer Protocol (SMTP), Domain Network System (DNS) protocol, Common Management Interface Protocol (CMIP), Transmission Control Protocol and Internet Protocol (TCP/IP), User Datagram Protocol (UDP), Long Term Evolution (LTE) communication protocols, or any combination thereof.
In some aspects of the present disclosure, the communication data may be transmitted or received via at least one shared downlink channel 108 of a number of downlink channels in a communication network. The shared downlink channel 108 may include, but is not limited to, a wireless channel, a wired channel, a combination of wireless and wired channel thereof. The wireless or wired channel may be associated with a data standard which may be defined by one of a Local Area Network (LAN), a Personal Area Network (PAN), a Wireless Local Area Network (WLAN), a Wireless Sensor Network (WSN), Wireless Area Network (WAN), Wireless Wide Area Network (WWAN), a metropolitan area network (MAN), a satellite network, the Internet, an optical fiber network, a coaxial cable network, an infrared (IR) network, a radio frequency (RF) network, and a combination thereof. Aspects of the present disclosure are intended to include and/or otherwise cover any type of communication channel, including known, related art, and/or later developed technologies.
The receiver 106 may be configured to receive the signals. Specifically, the receiver 106 may be configured to receive the signals that may be transmitted by the base station over the shared downlink channel 108. The signals may include data i.e., received data. The signals (received data) may be received at a point i.e., at a received symbol point.
The receiver 106 may include processing circuitry 110. The processing circuitry 110 may be configured to estimate a decoded symbol point corresponding to the received data. The processing circuitry 110 may be further configured to determine a distance between the decoded symbol point and the received symbol point. The processing circuitry 110 may be further configured to initialize a set of neighboring constellation points when the distance is greater than a predefined threshold. The processing circuitry 110 may be further configured to select an optimal decoded symbol point from the set of neighboring constellation points upon initialization of the neighboring constellation points. The processing circuitry 110 may be configured to formulate a decision metric for each possible symbol that may be intended for the target user. Specifically, the processing circuitry 110 may formulate the decision metric for each possible symbol that may be intended for the target user based on the determined distances. The decision metric may incorporate factors that may be selected from one of, the distances to neighboring constellation points, the signal-to-interference-plus-noise ratio (SINR), and other channel conditions. The processing circuitry 110 may be configured to select the optimal decoded symbol point by way of the decision metric. To select the optimal decoded symbol point, the processing circuitry 110 may be configured to determine a probability of correctness of the decoded symbol. The probability of correctness of the decoded symbol may be indicative of a degree of correctness of whether the decoded symbol is intended for the target user or not. The processing circuitry 110 may be configured to determine the probability of correctness by considering interference from neighboring users.
The processing circuitry 110 may include suitable logic, instructions, circuitry, interfaces, and/or codes for executing various operations. In some aspects of the present disclosure, the processing circuitry 110 may utilize one or more processors such as Arduino or raspberry pi or the like. Examples of the processing circuitry 110 may include, but not limited to, an application-specific integrated circuit (ASIC) processor, a reduced instruction set computing (RISC) 10 processor, a complex instruction set computing (CISC) processor, a field-programmable gate array (FPGA), a Programmable Logic Control unit (PLC), and the like. Aspects of the present disclosure are intended to include or otherwise cover any type of processing circuitry 110 including known, related art, and/or later developed processing units.
The processing circuitry 110 may be further configured to determine the distance between the decoded symbol point and the received symbol point, initialize the set of neighboring constellation points, and select the optimal decoded symbol point when the distance between the decoded symbol point and the received symbol point is greater than the predefined threshold. Specifically, the processing circuitry 110 may be configured to reiterate determining the distance, initializing the set of neighboring constellation points, and selecting the optimal decoded symbol point until the distance between the decoded symbol point and the received symbol point is less than the predefined threshold value. In each reiteration of determination of the distance, initialization the set of neighboring constellation points, and selection of the optimal decoded symbol point, the processing circuitry 110 may be configured to replace the decoded symbol point by the optimal decoded symbol point.
In some embodiments of the present disclosure, the set of neighboring constellation points may have a predefined size. The predefined size of the set of neighboring constellation points may depend on a modulation technique that may be employed by the base station 102. In some examples of the present disclosure, the modulation technique that may be employed by the base station 102 for the downlink transmission may include, but not limited to, a Quadrature Amplitude Modulation (QAM) technique.
In some embodiments of the present disclosure, the processing circuitry 110 may be configured to determine the distances between the received signal point and constellation points of neighboring users. Specifically, the processing circuitry 110 may be configured to determine the distances between the received signal point and the constellation points of neighboring users by way of a distance metric, such as, Euclidean distance in a complex signal space. The processing circuitry 110 may be further configured to perform iterative refinement of symbol selection. The decision metric and optimal decoded symbol selection process may be iteratively refined based on feedback from previous iterations.
The processing circuitry 110 may be configured to one of, (i) determine a power allocation coefficient and (ii) label the estimated decoded symbol point as the optimal decoded symbol point, when the distance is less than or equal to the predefined threshold. The processing circuitry 110 may be further configured to determine whether a signal from a target user is detected or not. Specifically, the processing circuitry 110 may be configured to determine the power allocation coefficient when the signal from the target user is not detected. The processing circuitry 110 may be configured to multiply the power allocation coefficient to the received data. Specifically, the processing circuitry 110, upon multiplying the power allocation coefficient with the received data, may be configured to facilitate detection of the signal from the target user.
The processing circuitry 110 may be further configured to label the estimated decoded symbol point as the optimal decoded symbol point. Specifically, the processing circuitry 110 may be configured to label the estimated decoded symbol point as the optimal decoded symbol point when the signal from the target user is detected.
In some embodiments of the present disclosure, the processing circuitry 110 may be further configured to employ a reliable region concept that may require a reliable region. The reliable region concept may facilitate detection of the decoded symbol point and iterative interference cancellation. The reliable region may represent an area within a signal space where the received symbol may be reliably detected and decoded.
In some embodiments of the present disclosure, the processing circuitry 110 may be further configured to employ a predefined stopping criterion that may facilitate the iterative interference cancellation. The predefined stopping criterion may be based on one of, (i) quality of the signals and (ii) maximum number of iterations.
FIG. 2 illustrates a block diagram of the processing circuitry 110, in accordance with an embodiment of the present disclosure. The processing circuitry 110 may include a plurality of engines to facilitate various operations/functions of the processing circuitry 110. For example, the processing circuitry 110 may include an estimation engine 202, a distance determination engine 204, an initialization engine 206, a selection engine 208, a reiteration engine 210, a signal detection engine 212, a power allocation engine 214, and a label engine 216.
The estimation engine 202, the distance determination engine 204, the initialization engine 206, the selection engine 208, the reiteration engine 210, the signal detection engine 212, the power allocation engine 214, and the label engine 216 may be communicatively coupled to each other by way of a communication bus 218. The communication bus 218 may facilitate the estimation engine 202, the distance determination engine 204, the initialization engine 206, the selection engine 208, the reiteration engine 210, the signal detection engine 212, the power allocation engine 214, and the label engine 216 to exchange information associated with the system 100 to each other.
The estimation engine 202 may be configured to facilitate the processing circuitry 110 to estimate the decoded symbol point corresponding to the received data.
The distance determination engine 204 may be configured to facilitate the processing circuitry 110 to determine the distance between the decoded symbol point and the received symbol point.
The initialization engine 206 may be configured to facilitate the processing circuitry 110 to initialize the set of neighboring constellation points when the distance is greater than the predefined threshold.
The selection engine 208 may be configured to facilitate the processing circuitry 110 to select the optimal decoded symbol point from the set of neighboring constellation points upon initialization of the neighboring constellation points. The selection engine 208 may be further configured to facilitate the processing circuitry 110 to formulate a decision metric for each possible symbol that may be intended for the target user. Specifically, the processing circuitry 110 may formulate the decision metric for each possible symbol that may be intended for the target user based on the determined distances. The decision metric may incorporate factors that may be selected from one of, the distances to neighboring constellation points, the signal-to-interference-plus-noise ratio (SINR), and other channel conditions. The processing circuitry 110 may be configured to select the optimal decoded symbol point by way of the decision metric. To select the optimal decoded symbol point, the processing circuitry 110 may be configured to determine the probability of correctness of the decoded symbol.
The reiteration engine 210 may be configured to facilitate the processing circuitry 110 to reiterate (i) determination determine the distance between the decoded symbol point and the received symbol point, (ii) initialization of the set of neighboring constellation points, and (iii) selection of the optimal decoded symbol point when the distance between the decoded symbol point and the received symbol point is greater than the predefined threshold.
Specifically, the reiteration engine 210 may be configured to facilitate the processing circuitry 110 to reiterate (i) determination of the distance, (ii) initialization of the set of neighboring constellation points, and (iii) selection of the optimal decoded symbol point until the distance between the decoded symbol point and the received symbol point is less than the predefined threshold value. In each reiteration of determination of the distance, initialization the set of neighboring constellation points, and selection of the optimal decoded symbol point, the processing circuitry 110 may be configured to replace the decoded symbol point by the optimal decoded symbol point.
The signal detection engine 212 may be configured to facilitate the processing circuitry 110 to determine whether the signal from the target user is detected or not. Specifically, the signal detection engine 212 may be configured to facilitate the processing circuitry 110 to determine whether the signal from the target user is detected or not when the distance is less than or equal to the predefined threshold.
The power allocation engine 214 may be configured to facilitate the processing circuitry 110 to determine the power allocation coefficient when the distance is less than or equal to the predefined threshold. Specifically, the power allocation engine 214 may be configured to facilitate the processing circuitry 110 to determine the power allocation coefficient when the signal from the target user is not detected. The power allocation engine 214 may be further configured to facilitate the processing circuitry 110 to multiply the power allocation coefficient to the received data. Specifically, the power allocation engine 214 may be configured to facilitate the processing circuitry 110 to multiply the power allocation coefficient to the received data that may further facilitate detection of the signal from the target user.
The label engine 216 may be configured to facilitate the processing circuitry 110 to label the estimated decoded symbol point as the optimal decoded symbol point. Specifically, the label engine 216 may be configured to facilitate the processing circuitry 110 to label the estimated decoded symbol point as the optimal decoded symbol point when the signal from the target user is detected.
FIG. 3 illustrates a flowchart of a method 300 for selecting the optimal decoded symbol point in the multi-user downlink NOMA communication network, in accordance with an embodiment of the present disclosure. The method 300 may include the following steps for selecting the optimal decoded symbol point in the multi-user downlink NOMA communication network.
At step 302, the system 100 may be configured to transmit the signals over the shared downlink channel 108. Specifically, the system 100, by way of the users 104, may be configured to transmit the signals over the shared downlink channel 108. The users 104 may be served by the base station 102.
At step 304, the system 100 may be configured to estimate the decoded symbol point corresponding to the received data. Specifically, the system 100, by way of the processing circuitry 110 of the receiver 106, may be configured to estimate the decoded symbol point corresponding to the received data.
At step 306, the system 100 may be configured to determine the distance between the decoded symbol point and the received symbol point. Specifically, the system 100, by way of the processing circuitry 110, may be configured to determine the distance between the decoded symbol point and the received symbol point.
At step 308, the system 100 may be configured to initialize the set of neighboring constellation points when the distance is greater than the predefined threshold. Specifically, the system 100, by way of the processing circuitry 110, may be configured to initialize the set of neighboring constellation points when the distance is greater than the predefined threshold.
At step 310, the system 100 may be configured to select the optimal decoded symbol point from the set of neighboring constellation points. Specifically, the system 100, by way of the processing circuitry 110, may be configured to select the optimal decoded symbol point from the set of neighboring constellation points.
At step 312, the system 100 may be configured to reiterate steps from the step 306 to the step 310 until the distance is less than the predefined threshold. Specifically, the system 100, by way of the processing circuitry 110, may be configured to reiterate the steps from the step 306 to the step 310 until the distance is less than the predefined threshold. In each reiteration, the decoded symbol point may be replaced by the optimal decoded symbol point.
At step 314, the system 100 may be configured to determine whether the signal from the target user is detected or not. Specifically, the system 100, by way of the processing circuitry 110, may be configured to determine whether the signal from the target user is detected or not. The processing circuitry 110 determines whether the signal from the target user is detected or not when the distance is less than or equal to the predefined threshold.
At step 316, the system 100 may be configured to determine the power allocation coefficient when the distance is less than or equal to the predefined threshold. Specifically, the system 100, by way of the processing circuitry 110, may be configured to determine the power allocation coefficient when the distance is less than or equal to the predefined threshold. The processing circuitry 110 may be configured to determine the power allocation coefficient when the signal from the target user is not detected. The processing circuitry 110 may be further configured to multiply the power allocation coefficient to the received data. Specifically, the processing circuitry 110 may be configured to multiply the power allocation coefficient to the received data that may further facilitate detection of the signal from the target user.
At step 318, the system 100 may be configured to label the estimated decoded symbol point as the optimal decoded symbol point. Specifically, the system 100, by way of the processing circuitry 110, may be configured to label the estimated decoded symbol point as the optimal decoded symbol point when the signal from the target user is detected.
The foregoing discussion of the present disclosure has been presented for purposes of illustration and description. It is not intended to limit the present disclosure to the form or forms disclosed herein. In the foregoing Detailed Description, for example, various features of the present disclosure are grouped together in one or more aspects, configurations, or aspects for the purpose of streamlining the disclosure. The features of the aspects, configurations, or aspects may be combined in alternate aspects, configurations, or aspects other than those discussed above. This method of disclosure is not to be interpreted as reflecting an intention the present disclosure requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed aspect, configuration, or aspect. Thus, the following claims are hereby incorporated into this Detailed Description, with each claim standing on its own as a separate aspect of the present disclosure.
Moreover, though the description of the present disclosure has included description of one or more aspects, configurations, or aspects and certain variations and modifications, other variations, combinations, and modifications are within the scope of the present disclosure, e.g., as may be within the skill and knowledge of those in the art, after understanding the present disclosure. It is intended to obtain rights which include alternative aspects, configurations, or aspects to the extent permitted, including alternate, interchangeable and/or equivalent structures, functions, ranges or steps to those claimed, whether or not such alternate, interchangeable and/or equivalent structures, functions, ranges or steps are disclosed herein, and without intending to publicly dedicate any patentable subject matter.
, Claims:1. A multi-user downlink NOMA communication system (100) comprising:
a base station (102);
a plurality of users (104a-104n) served by the base station (102) transmitting signals over a shared downlink channel (108);
a receiver (106) associated with each user of the plurality of users, and configured to:
a) estimate a decoded symbol point corresponding to received data;
b) determine a distance between the decoded symbol point and a received symbol point;
c) initialize a set of neighboring constellation points when the distance is greater than a predefined threshold;
d) select an optimal decoded symbol point from the set of neighboring constellation points;
e) reiterate from b) to d) until the distance is less than the predefined threshold, wherein, in each reiteration, the decoded symbol point is replaced by the optimal decoded symbol point.

2. The multi-user downlink NOMA communication system (100) as claimed in claim 1, wherein the set of neighboring constellation points has a predefined size that depends on a modulation technique employed by the base station (102).

3. The multi-user downlink NOMA communication system (100) as claimed in claim 2, wherein the modulation technique employed by the base station (102) for the downlink transmission is Quadrature Amplitude Modulation (QAM) technique.

4. The multi-user downlink NOMA communication system (100) as claimed in claim 1, wherein when the distance is less or equal to the predefined threshold, the receiver (106) is configured to multiply a power allocation coefficient to the received data when a signal from a target user is not detected such that the power allocation coefficient facilitates detection of the signal from the target user.

5. The multi-user downlink NOMA communication system (100) as claimed in claim 1, wherein when the distance is less or equal to the predefined threshold, the receiver (106) is configured to label the estimated decoded symbol point as the optimal decoded symbol point when a signal from a target user is detected.

6. The multi-user downlink NOMA communication system (100) as claimed in claim 1, wherein the receiver (106) is configured to formulate a decision metric for each possible symbol intended for the target user based on the determined distances.

7. The multi-user downlink NOMA communication system (100) as claimed in claim 6, wherein the decision metric incorporates factors selected from one of, the distances to neighboring constellation points, the signal-to-interference-plus-noise ratio (SINR), and other channel conditions.

8. The multi-user downlink NOMA communication system (100) as claimed in claim 1, wherein the receiver (106) is further configured to employ a reliable region concept that requires a reliable region such that the reliable region concept facilitates detection of the decoded symbol point and iterative interference cancellation, wherein the reliable region represents an area within a signal space where the received symbol point is reliably detected and decoded.

9. The multi-user downlink NOMA communication system (100) as claimed in claim 8, wherein the receiver (106) is further configured to employ a predefined stopping criterion to facilitate the iterative interference cancellation, wherein the predefined stopping criterion is based on one of, (i) quality of the signals and (ii) maximum number of iterations.

10. The multi-user downlink NOMA communication system (100) as claimed in claim 6, wherein the receiver (106) is configured to select the optimal decoded symbol point by way of the decision metric, wherein to select the optimal decoded symbol point, the receiver (106) is configured to determine a probability of correctness of the decoded symbol.

11. A method (300) for selecting an optimal decoded symbol point in a multi-user downlink NOMA communication network, the method (300) comprising:
transmitting (302), by way of a plurality of users served by a base station (102), signals over a shared downlink channel (108);
estimating (304), by way of a receiver (106) associated with each user of the plurality of users, a decoded symbol point corresponding to received data;
determining (306), by way of the receiver (106), a distance between the decoded symbol point and the received symbol point;
initializing (308), by way of the receiver (106), a set of neighboring constellation points when the distance is greater than a predefined threshold;
selecting (310), by way of the receiver (106), the optimal decoded symbol point from the set of neighboring constellation points;
reiterating (312) steps from the step (306) to the step (310) until the distance is less than the predefined threshold, wherein, in each reiteration, the decoded symbol point is replaced by the optimal decoded symbol point.