Patent Publication Number: US-10779154-B2

Title: Apparatuses and methods for discovery message formats distinction

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of patent application Ser. No. 15/035,687 filed May 10, 2016, entitled “APPARATUSES AND METHODS FOR DISCOVERY MESSAGE FORMATS DISTINCTION” which is a U.S. National Stage Application of PCT/SE2016/050219, filed Mar. 17, 2016, entitled “APPARATUS AND METHODS FO DISCOVERY MESSAGE FORMATS DISTINCTION” which claims priority to and the benefit of the filing date of U.S. Provisional Application No. 62/137,868, filed on Mar. 25, 2015, all of which are incorporated herein by reference in their entireties. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a first communication device and a method therein, of receiving a discovery or a Device-to-Device (D2D) discovery message from a second communication device and identifying a format of the discovery message. The present disclosure also relates to a second communication device and a method therein for generating a discovery or D2D message according to a message format and to transmit the discovery or D2D message to the first communication device. 
     BACKGROUND 
     Communication devices such as wireless device are also known as e.g. User Equipments (UE), mobile terminals, wireless terminals and/or mobile stations. Terminals are enabled to communicate wirelessly in a cellular communications network or wireless communication system, sometimes also referred to as a cellular radio system or cellular networks. The communication may be performed e.g. between two wireless devices, between a wireless device and a regular telephone and/or between a wireless device and a server via a Radio Access Network (RAN) and possibly one or more core networks, comprised within the cellular communications network. 
     Wireless devices may further be referred to as mobile telephones, cellular telephones, laptops, or surf plates with wireless capability, just to mention some further examples. The terminals in the present context may be, for example, portable, pocket-storable, hand-held, computer-comprised, or vehicle-mounted mobile devices, enabled to communicate voice and/or data, via the RAN, with another entity, such as another terminal or a server. 
     The cellular communications network covers a geographical area which is divided into cell areas, wherein each cell area being served by an access node such as a base station, e.g. a Radio Base Station (RBS), which sometimes may be referred to as e.g. “eNB”, “eNodeB”, “NodeB”, “B node”, or BTS (Base Transceiver Station), depending on the technology and terminology used. The base stations may be of different classes such as e.g. macro eNodeB, home eNodeB or pico base station, based on transmission power and thereby also cell size. A cell is the geographical area where radio coverage is provided by the base station at a base station site. One base station, situated on the base station site, may serve one or several cells. Further, each base station may support one or several communication technologies. The base stations communicate over the air interface operating on radio frequencies with the terminals within range of the base stations. In the context of this disclosure, the expression Downlink (DL) is used for the transmission path from the base station to the mobile station. The expression Uplink (UL) is used for the transmission path in the opposite direction i.e. from the mobile station to the base station. 
     In 3 rd  Generation Partnership Project (3GPP) Long Term Evolution (LTE), base stations, which may be referred to as eNodeBs or even eNBs, may be directly connected to one or more core networks. 
     3GPP LTE radio access standard has been developed in order to support high bitrates and low latency both for uplink and downlink traffic. All data transmission is in LTE controlled by the radio base station. 
     Recent developments of the 3GPP LTE facilitate accessing local Internet Protocol (IP) based services in the home, office, public hot spot or even outdoor environments. One of the important use cases for the local IP access and local connectivity involves the direct communication between devices in the close proximity, typically less than a few 10s of meters, but sometimes up to a few hundred meters, of each other. 
     This direct mode or Device-to-Device (D2D) enables a number of potential gains over the traditional cellular technique, because D2D wireless devices are much closer to one another than cellular wireless devices that have to communicate via cellular Access Point (AP), e.g., eNB:
         Capacity gain: First, radio resources, e.g., Orthogonal Frequency Division Multiplexing (OFDM) resource blocks, between the D2D and cellular layers may be reused, i.e., reuse gain. Second, a D2D link uses a single hop between the transmitter and receiver points as opposed to the 2-hop link via a cellular AP, i.e., hop gain.   Peak rate gain: due to the proximity and potentially favorable propagation conditions, high peak rates may be achieved, i.e., proximity gain.   Latency gain: When the wireless devices, e.g., UEs, communicate over a direct link, eNB forwarding is short cut and the end-to-end latency may decrease.       

     The Feasibility Study on Proximity-based Services, in 3GPP, feasibility study for Proximity Services (ProSe), has identified services that may be provided by the 3GPP system based on UEs being in proximity to each other. The identified areas comprise services related to commercial services and Public Safety (PS) that may be of interest to operators and users. PS may comprise, e.g., all first responders in case of an emergency such as police, firemen, etc. Commercial services may comprise any consumer application that is not a PS device. Commercial services may also be referred to herein as non-PS services. The objectives of this feasibility study are to evaluate LTE D2D proximity services, as indicated in Table 1, indicates the type of activity to be performed by a wireless device, and the the coverage condition in which the activity is performed by the wireless device, that is whether the wireless device is within or outside of network coverage. 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                   
                   
                 Outside 
               
               
                   
                   
                 Within network 
                 network 
               
               
                   
                   
                 coverage 
                 coverage 
               
               
                   
                   
               
             
            
               
                   
                 Discovery 
                 Non public safety  
                 Public safety 
               
               
                   
                   
                 &amp; public safety 
                 only 
               
               
                   
                   
                 requirements 
                   
               
               
                   
                 Direct 
                 At least public 
                 Public safety 
               
               
                   
                 Communication 
                 safety requirements 
                 only 
               
               
                   
                   
               
            
           
         
       
     
     For a D2D system, message detection is a performance aspect, for which it is desirable to both increase the message detection probability and to reduce the false alarm probability. 
     Peer discovery may be the first step in the establishment of a D2D link, i.e., the devices discover the presence of their peer, which has partly similar functionality as the cell search procedure in LTE. Discovery may be made possible by one party sending a message signal, i.e., a discovery D2D message, and the other party scanning for such a message. By measuring the quality of the received message signal, estimation may be made whether the radio channel is good enough to establish a D2D link. Discovery messages may be transmitted periodically, carrying information about the identity of the transmitter UE. In the general procedure a neighbor wireless device is “discovered” once a message carrying the wireless device&#39;s identity is detected. 
     In more detail, the discovery procedure may be divided into different types in different dimensions. For example it may be divided into: 
     1. Open Discovery: where the Transmitter (Tx) wireless device may be discovered by all neighboring wireless devices in the proximity; 
     2. Restricted Discovery: where the Tx wireless device target at specific Receiver (Rx) wireless device(s), i.e., may only be discovered by specific Rx wireless device(s). 
     Thus, a discovery message, as used herein, may be understood as a message sent by a wireless device to be discovered by other radio network node/s, or to discover other radio network node/s, such as wireless device/s, over a D2D link. 
     The content of a discovery message, from a L1 perspective, is known as the payload of a discovery message. The payload is the sum of all the individual fields, each comprising a particular type of information, within the payload. The set of fields, i.e., payload fields, and corresponding length within the payload, is known as the payload format. The number of bits of the payload is known as the payload size. 
     The payload format may be different for different types of D2D discovery messages, as shown below. 
     1. For a non-public safety open discovery use case, the expected size of the information carried in discovery messages is currently assumed to be 192 bits, as shown in Table 2 below, which shows, for three different payload fields of information carried in discovery messages, the assessed length in number of bits. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                 Payload 
                 Assessed 
               
               
                   
                 Field 
                 Length 
               
               
                   
                   
               
             
            
               
                   
                 Prose 
                 160 bits  
               
               
                   
                 Application 
                   
               
               
                   
                 Code 
                   
               
               
                   
                 ProSe 
                  8 bits 
               
               
                   
                 Function 
                   
               
               
                   
                 IDentifier (ID) 
                   
               
               
                   
                 PLMN ID 
                 24 bits 
               
               
                   
                   
               
            
           
         
       
     
     2. For a Public safety case, the message structure depicted in Table 3 is expected. Table 3, in addition to the columns shown in Table 2, shows the payload, the the assessed length and the purpose. 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 3 
               
               
                   
                   
               
               
                   
                 Payload 
                 Assessed 
                   
               
               
                   
                 Field 
                 Length 
                 Purpose 
               
               
                   
                   
               
             
            
               
                   
                 Source L2 
                 e.g. 48 
                 To identify a single 
               
               
                   
                 ID/Prose 
                 bits 
                 UE source of the 
               
               
                   
                 UE ID of 
                   
                 information in the 
               
               
                   
                 source 
                   
                 message. This may 
               
               
                   
                   
                   
                 be used for 
               
               
                   
                   
                   
                 subsequent 
               
               
                   
                   
                   
                 communication or 
               
               
                   
                   
                   
                 to send a reply in 
               
               
                   
                   
                   
                 Model B of 
               
               
                   
                   
                   
                 operation 
               
               
                   
                 Destination 
                 e.g. 48 
                 To identify a single 
               
               
                   
                 L2 ID 
                 bits 
                 UE or group of UEs 
               
               
                   
                   
                   
                 that are intended 
               
               
                   
                   
                   
                 recipients of the 
               
               
                   
                   
                   
                 information (a 
               
               
                   
                   
                   
                 single UE in 
               
               
                   
                   
                   
                 responses for 
               
               
                   
                   
                   
                 model B). 
               
               
                   
                 Message 
                  8 bits 
                 Type of discovery 
               
               
                   
                 type 
                   
                 message 
               
               
                   
                 Prose 
                 64 bits 
                 Needed to perform 
               
               
                   
                 Application 
                   
                 matching to the 
               
               
                   
                 ID 
                   
                 required service 
               
               
                   
                   
                   
                 Set/Discovery 
               
               
                   
                   
                   
                 criterion 
               
               
                   
                 UE mode 
                  2 bits 
                 Defines whether a 
               
               
                   
                 of 
                   
                 Public safety 
               
               
                   
                 operation 
                   
                 ProSe UE is acting 
               
               
                   
                   
                   
                 as a UE-to-network 
               
               
                   
                   
                   
                 relay, UE-to-UE or 
               
               
                   
                   
                   
                 both or not acting 
               
               
                   
                   
                   
                 as relay 
               
               
                   
                 PLMN ID 
                 24 bits 
                 The PLMN ID the 
               
               
                   
                 (Public 
                   
                 ProSe UE is 
               
               
                   
                 Land 
                   
                 attached to. 
               
               
                   
                 Mobile 
                   
                   
               
               
                   
                 Network) 
                   
                   
               
               
                   
                 Status bits 
                  4 bits 
                 Some 
               
               
                   
                   
                   
                 status/maintenance 
               
               
                   
                   
                   
                 flags. 
               
               
                   
                   
               
            
           
         
       
     
     3. Discovery message for relay UE discovery where a UE is either announcing itself as a relay or requesting connectivity to a relay node. Such different relay discovery messages may be associated to different discovery message types or formats e.g. relay-related message formats. 
     The terms Public Safety (PS) and National Security and Public Safety (NSPS), as used herein, indicate public safety. The terms consumer and commercial, as used herein, are meant to indicate non-public safety applications. 
     If considering that the discovery message may have different payload sizes. It may cause ambiguity to the receiver (Rx) due to e.g.: a mix of consumer, public safety, relay UEs discoverable on the same carrier; or that the Rx does not know if a carrier is commercial, PS or acting as a relay. 
     One solution would be to let Layer 1 at the receiver decode all received messages depending on the different types of messages and based on different assumption of the message format. However, this would lead to higher complexity and an increase in computational burden on the receiver. Further, if e.g. the payload size is the same but the payload field format is different, the Layer 2/3 of the receiver would not know how to interpret the fields of the message, thus causing ambiguity at the receiver. Layer 1 (L1) is a physical layer, wherein L2 is a Medium Access Control (MAC) layer, and wherein L3 is a Radio Resource Control (RRC) layer and a Packet Data Convergence Protocol (PDCP) layer. 
     SUMMARY 
     It is an object of embodiments herein to solve the above problems and to improve the performance in a wireless communications network by providing methods and first and second communication devices/apparatuses enabling identification of a format of a discovery or D2D message already at Layer 1 enabling the first and second communication devices to distinguish between different discovery formats or D2D message formats efficiently thereby reducing complexity, power consumption and processing time of the first communication device and of the second communication device. 
     According to an aspect of embodiments herein, there is provided a method in a first communication device/apparatus, the method comprising: receiving, from a second communication device/apparatus, a discovery or D2D message at Layer 1 of the first communication device; identifying a message format of the received discovery or D2D message and transmitting decoded discovery of D2D message to upper layer(s). According to an example, the decoded message to upper layer(s) may include an indication of the identified message format enabling the higher layer(s) of the first communication device to identity the message format. Example of discovery or D2D message formats may include a format for a relay discovery announcement; a format for a relay discovery request; a format for a discovery public safety message or a format for a discovery consumer related message. 
     According to an exemplary embodiment, identification of the message format may be performed before decoding of the received message. Hence, according to another aspect of embodiments herein, the method comprising: after identification of the message format of the discovery or D2D message received at Layer 1 from the second communication device/apparatus; decoding of the received discovery or D2D message according to the identified message format is performed followed by transmitting the decoded message to upper layers. As mentioned above, the decoded message to upper layers may include an indication of the identified message format enabling the higher layers of the first communication device to identity the message format. 
     According to an exemplary embodiment, identification of the message format may be performed after decoding of the received message. Hence, according to another aspect of embodiments herein, the method comprising: after receiving the discovery or D2D message at Layer 1, decoding the received message; identifying the message format of the decoded discovery or D2D message and transmitting the decoded message to upper layers. As mentioned above, the decoded message to upper layers may include an indication of the identified message format enabling the higher layers of the first communication device to identity the message format. 
     According to another aspect of embodiments herein, there is provided a first communication device comprising: a processing circuit or a processing module or a processor or means configured to identify a message format of a discovery or D2D message received, by means of a receiver circuit or receiver module, at Layer 1 from a second communication device/apparatus. The processing circuit or processing module or processor or means is further configured to transmit decoded discovery or D2D message to upper layers of the first communication device. According to an example, the decoded message to upper layer(s) may include an indication of the identified message format enabling the higher layers of the first communication device to identity the message format. Example of discovery or D2D message formats may include a format for a relay discovery announcement; a format for a relay discovery request; a format for a discovery public safety message or a format for a discovery consumer related message. 
     According to an exemplary embodiment, the processing circuit or a processing module or processor or means is configured to identify the message format before decoding of the received message. Hence, according to another aspect of embodiments herein, the first communication device is configured to: after identification of the message format of the discovery or D2D message received at Layer 1 from the second communication device/apparatus; decode, by means of the processing circuit or a processing module or processor or means, the received discovery or D2D message according to the identified message format followed by transmitting, by means of the processor, the decoded message to upper layers. As mentioned above, the decoded message to upper layers may include an indication of the identified message format enabling the higher layers of the first communication device to identity the message format. 
     According to an exemplary embodiment, the processing circuit or a processing module or a processor or means is configured to identify the message format after decoding of the received message by means of the processing circuit or processing module or processor or means. Hence, according to another aspect of embodiments herein, the first communication device is configured, by means of the processing circuit or processing module or processor or means, to decode the received message; identify the message format of the decoded discovery or D2D message and transmit the decoded message to upper layers. As mentioned above, the decoded message to upper layers may include an indication of the identified message format enabling the higher layers of the first communication device to identity the message format. 
     According to another aspect of embodiments herein, there is provided a method in a second communication device/apparatus, the method comprising: obtaining, from higher layer(s), at Layer 1 of the second communication device a discovery message for physical layer processing. A format of the discovery message is also indicated to Layer 1 by higher layer(s); the message further comprising encoding the received message according to the indicated message format and transmitting the encoded discovery message to a first communication device. 
     According to another aspect of embodiments herein, there is provided a second communication device/apparatus comprising: a processing circuit or a processing module or a processor or means configured to obtain, from higher layer(s), at Layer 1 of the second communication device a discovery or D2D message for physical layer processing and a format of the discovery or D2D message is indicated to Layer 1 by higher layer(s); the processing circuit or processing module or processor or means is further configured to encode the obtained message according to the indicated message format and the second communication device comprises a transmitter circuit or transmitter module configured to transmit the encoded discovery or D2D message to a first communication device. 
     An advantage with the embodiments herein is to avoid ambiguity of different message formats at the first and second communication device thereby reducing complexity, power consumption and processing time of the second communication device and first communication device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Examples of embodiments herein are described in more detail with reference to attached drawings in which: 
         FIG. 1  is a schematic block diagram illustrating in a wireless communications network wherein embodiments herein may be applied. 
         FIG. 2  is a flowchart depicting some exemplary embodiments of a method performed by a first communication device. 
         FIG. 3  is a flowchart depicting other exemplary embodiments of a method performed by the first communication device. 
         FIG. 4  is a flowchart depicting some embodiments of a method performed by the first communication device. 
         FIG. 5  is a flowchart depicting embodiments of a method performed by a second communication device. 
         FIG. 6  is a schematic block diagram illustrating embodiments of a first communication device, according to embodiments herein. 
         FIG. 7  is a schematic block diagram illustrating embodiments of a second communication device, according to embodiments herein. 
     
    
    
     DETAILED DESCRIPTION 
     In the following, a detailed description of the exemplary embodiments of the present invention is described in conjunction with the drawings, in several scenarios to enable easier understanding the solution(s) described herein. 
     Given that that the provision of LTE D2D proximity services, as indicated in Table 1, depends on the type of information associated with the messages to be sent by a second communication device, e.g., PS commercial or relay, it is beneficial for a first communication device to be able to distinguish the type of messages, associated with the service, each associated with a specific format. 
     The message payload may be different for different type of discovery or D2D messages in terms of different payload size and/or different payload field format. 
     As previously described, basing the distinction of the types of discovery messages on that the discovery message may have different payload size, may cause ambiguity to Rx (receiver), such as reception, due to, for example: 
     1) a mix of non-public safety, e.g., consumer, and public safety wireless devices are discoverable on the same carrier; 
     2) or that the Rx does not know if a carrier is non-public safety, e.g., commercial or PS. 
       FIG. 1  depicts a particular example of a wireless communications network  100 , sometimes also referred to as a cellular radio system, in which embodiments herein may be implemented and in which D2D communications may be used. The wireless communications network  100  may for example be a network such as a Long-Term Evolution (LTE), e.g. LTE Frequency Division Duplex (FDD), LTE Time Division Duplex (TDD), LTE Half-Duplex Frequency Division Duplex (HD-FDD), LTE operating in an unlicensed band, network comprising of any combination of Radio Access Technologies (RATs) such as e.g. Multi-Standard Radio (MSR) base stations, multi-RAT base stations etc., any 3rd Generation Partnership Project (3GPP) cellular network, WiFi networks, Worldwide Interoperability for Microwave Access (WiMax), 5G system or any cellular network or system. 
     The wireless communications network  100  comprises a radio network node  110  which may be base station such as, e.g., an eNB, eNodeB, or a Home Node B, a Home eNode B, femto Base Station, BS, pico BS, Transmission Point (TP), or any other network unit capable to serve a wireless device or a machine type communication device in a wireless communications network  100 . In some particular embodiments, the radio network node  110  may be a stationary relay node or a mobile relay node. 
     The wireless communications network  100  covers a geographical area which is divided into cell areas, wherein each cell area is served by a network node, although, one network node may serve one or several cells. In the non-limiting example depicted in  FIG. 1 , the network node  110  serves a cell  120 . The network node  110  may be of different classes, such as, e.g., macro eNodeB, home eNodeB or pico base station, based on transmission power and thereby also cell size. 
     A number of wireless devices are located in the wireless communications network  100 . In the example scenario of  FIG. 1 , only two D2D capable wireless devices are shown, wireless device  131  and wireless device  132 . The wireless device  132 , herein a first communication device, may be a mobile terminal, wireless terminal, mobile station, mobile telephone, cellular telephone, smart phone or a device-to-device (D2D) device which may operate as a relay D2D device for other D2D devices e.g. device  131 . The second wireless device  131 , herein a second communication device, may also be a mobile terminal, wireless terminal, mobile station, mobile telephone, cellular telephone, smart phone or a device-to-device (D2D) device which may operate as a relay D2D device for other D2D devices e.g. device  132 . Further examples of different wireless devices comprise laptops with wireless capability, Laptop Embedded Equipment (LEE), Laptop Mounted Equipment (LME), USB dongles, Customer Premises Equipment (CPE), modems, Personal Digital Assistants (PDA), or tablet computers, sometimes referred to as a surf plates with wireless capability or simply, tablets, Machine-to-Machine (M2M) capable devices or UEs, Machine Type Communication (MTC) devices such as sensors, e.g., a sensor equipped with UE, just to mention some examples. 
     The wireless devices  131  and  132  are capable of communicating using wireless D2D communication over a D2D link  140 . The wireless device  131  is configured to communicate with the network node  110  over radio link  151 . The radio network node  132  may communicate with the network node  110  over a radio link such as e.g. radio link  152 . 
     Embodiments herein provide methods that allow distinction between the D2D discovery message formats and address the issue listed previously. Any reference herein to Rx, or first communication device is understood to apply to wireless device such as wireless device  132 . Any reference herein to Tx or second communication device is understood to apply to wireless device such as the wireless device  131 . A reference herein to a discovery message, may be made by using the term “message” or “D2D message”. 
     In the following, embodiments herein are described by focusing on the case where different discovery or D2D message types are possible: For example, one for PS wireless device discovery, one for commercial wireless device discovery and one for relay discovery. However, any of the techniques may be readily applied to additional message formats, both for discovery or other purposes. A discovery D2D message format may also be referred to herein as a discovery message type. 
     For example a message format may be used for relay device discovery, where a wireless device is either announcing itself as a relay or requesting connectivity to a relay node. Such relay discovery messages may be associated to different discovery message types or formats. Additional discovery messages may relate to group-check for discovery of groups of users or devices involved in a group or broadcast communication. 
     The following embodiments provide ways to differentiate between different discovery message formats. This is performed at Layer 1 (L1) at the first communication device receiving the discovery D2D message. It should be noted that this is possible even before decoding, such as channel decoding of the discovery message content. 
     At the second communication device, the higher layers may indicate to L1 the format of the discovery message to be transmitted, so that L1 may apply the correct processing and transmission parameters. 
     At the first communication device, L1 may indicate to higher layers the detected format of the discovery message, so that higher layers may interpret the content fields correctly. 
     According to an embodiment, the mapping between the processing and transmission parameters of discovery messages and the formats of discovery messages may be determined by a configuration known by both the first and second communication devices, or may be at least partly configured by some network node (e.g. a eNB), such as the network node  110 . 
     The term “format of the discovery D2D message” or “message format” may indicate e.g. the payload size and the mapping of different information fields of the payload. 
     Some embodiments are provided that may be applicable for the scenario where the discovery message payload sizes are different for different formats. In this case, some methods are addressed in the following to avoid the decoding complexity. However, the application of these embodiments is not limited to the case where payload sizes are different. 
     Referring to  FIG. 2  there is illustrated the main steps of a procedure/method performed by a first communication device e.g. wireless device  131  according to some exemplary embodiments herein. The method comprising: 
     ( 201 ) receiving, from a second communication device, a discovery or D2D message at Layer 1 of the first communication device; 
     ( 202 ) identifying a message format of the received message; 
     ( 203 ) decoding the received message according to the identified message format; and 
     ( 204 ) sending/transmitting the decoded message to higher layers (L2/L3) of the first communication device. 
     According to an example, the decoded message to upper layers may include an indication of the identified message format enabling the higher layers of the first communication device to identity the message format. As previously described, examples of discovery or D2D message formats may include a format for a relay discovery announcement; a format for a relay discovery request; a format for a discovery public safety message or a format for a discovery consumer related message. 
     According to an exemplary embodiment, identification of the message format may be performed by mapping the message format to at least one reference signal sequence associated with the received discovery message. For example, the first communication device may detect one or more parameters associated to one or several reference signal sequences and from such parameters determine the message format of the received discovery message. 
     For example, the first communication device may be pre-configured with at least one reference signal sequence and the mapping may be performed based on the reference signal sequence. For example, sequence  1  for message format  1 , sequence  2  for message format  2 , sequence  3  for message format  3 , etc. A sequence maybe a base sequence, a group sequence, a sequence identity, a scrambling sequence, a cyclic shift, an orthogonal cover code etc. It should be noted that identification may be performed during channel estimation. In this way, by correlating the received reference signal/message to different hypothesis (e.g. with sequence  1 , sequence  2  and/or sequence  3 ), the first communication device may know which format the received message uses. For example, if a relay announcement message received by the first communication device uses a distinguishable scrambling sequence, the first communication device may identify the received relay announcement message by associating it with the distinguishable scrambling sequence. 
     According to another exemplary embodiment, identification of the message format may be performed via a resource mapping scheme by mapping between resource mapping schemes of the discovery message and the associated message format. For example, mapping scheme  1  for message format  1 ; mapping scheme  2  for message format  2 , mapping scheme for message format  3  etc. An example of a mapping scheme may be a resource location of the message. For example, the messages of different formats may be located at different time/frequency locations in a subframe carrying the message. For example, a PS message may be located at resource pool  1 ; a commercial message may be located at resource pool  2  and a relay announcement message may be location at resource pool  3 . The resource pools may be mutually orthogonal to each other. Thus, depending on the resource location where the first communication device detects a certain discovery message, the message format is identified or obtained. 
     Another example of a mapping scheme may be guard period/subcarrier location. For example, the first communication device may identify the message format depending on the location of the guard period/subcarrier in the received discovery message as well as the length of the guard period/subcarrier. For example, in a resource unit comprising X subcarriers and Y symbols, where X and Y are design parameters, a guard period (in time) or guard band (in frequency) may be defined. The first communication device may identify the format of the received message including the guard time or guard period by e.g. determining the length of the guard period at the end of the message and then identify the format type. For example, the length of the guard period or guard band may be specific to the type of message received. 
     Another example of a mapping scheme is to make use of different cyclic prefix (CP) length for the identification. For example, different message formats may be associated to different CP lengths. As an example, a message format with a predefined length K may be identified as belonging to a PS message; a message format with a predefined length N may be identified as belonging to a commercial message; a message format with a predefined length M may be identified as belonging to relay message. K, N and M are design parameters or may be defined in a 3GPP standard specification. 
     In another exemplary embodiment, the second communication device/apparatus may provide the first communication device with information on the used message format by means of a dedicated signalling field that may be multiplexed with the discovery message that is received by the first communication device. 
     As previously described, the first communication device is configured to identify the message format of the received before decoding the receive message. In alternative exemplary embodiment, the receive device may attempt to decode the message prior to identifying the message format. This may be the case when the message payload size is unified. 
     Referring to  FIG. 3  there illustrated an example of the embodiment described above i.e. when the decoding is performed prior to identifying the message format. As shown, the method comprises: 
     ( 301 ) receiving, from a second communication device, a message at Layer 1; 
     ( 302 ) decoding the received message; 
     ( 303 ) identifying a message format of the received message; 
     Assuming that the received signal has been scrambled by the second communication device, the first communication device in this step may determine the message format by first descrambling the received message and perform a CRC (Cyclic Redundancy Check). Different scrambling schemes may be used. For example and as previously described, a mapping may be performed between a scrambling scheme and message format, e.g. scrambling scheme  1  for format  1  and scrambling scheme  2  for format  2  and scrambling scheme for format  3 . The first communication device is configured to perform the descrambling more than once according to different schemes for the different formats. Assuming that the CRC is successful, the received would identify the message format. 
     For example, the first communication device may perform CRC with PS discovery CRC and if the CRC fails, the first communication device continues by performing CRC with non-PS discovery CRC. If the CRC fails, the first communication device performs a CRC with relay announce CRC and if that fails, the UE performs CRC check with relay request CRC and if that succeeds the first communication device identifies the message format as belonging to a relay request message. 
     Detection or identification of the received signal or message at L1 is performed to differentiate the message formats e.g. a format of a relay announcement message; a format of a relay request message; a format of a non-PS or commercial message or a format of a PS message. The identification may be performed according to any of the previously described embodiments. 
     When the message format has been identified, the method further comprises as shown in  FIG. 3 , sending/transmitting ( 304 ) the decoded message to higher layers of the first communication device and optionally indicate the format message to the higher layers in order to avoid ambiguity of interpretation at the higher layers. 
     The first communication device may decide the order of CRC to be used based on the estimation of the possibility of message type being received. The first communication device may try the CRC in a decreasing order of the corresponding possibility. E.g. the first communication device may maintain a table as below. In this case, the order of CRC to be checked is relay announcement firstly, then commercial discovery, then relay request; and the first communication device may decide not try CRC for PS discovery: 
     
       
         
           
               
               
               
             
               
                   
                   
               
               
                   
                 Message type 
                 possibility 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 relay announcement 
                 10 
               
               
                   
                 relay request 
                 3 
               
               
                   
                 commercial discovery 
                 5 
               
               
                   
                 PS discovery 
                 0 
               
               
                   
                   
               
            
           
         
       
     
     When a certain type of message is expected by the first communication device, the corresponding CRC may increase. E.g. a discovery message may be repeated several times with some pre-defined pattern both in time domain and in frequency domain. If the first communication device has received commercial discovery messages before, and according the pattern of the message being transmitted, is expecting to receive a commercial discovery message within a predefined time interval, the first communication device may check commercial discovery message CRC earlier than others. If CRC for commercial discovery message fails, the first communication device may try other CRCs for other types of messages. 
     Assuming that the first communication device is out of coverage, the possibility or probability that PS discovery message is received first is more prioritized than the possibility for receiving a commercial discovery message since commercial discovery is not supported in out of coverage scenarios. 
     Assuming that a first communication device is acting as a ProSe or D2D relay, the possibility for relay request should increase. When a first communication device is not acting as a ProSe or D2D relay, the possibility for relay request should be 0. 
     Referring to  FIG. 4  there is illustrated main method steps performed by the first communication device according to previously described embodiments. 
     As shown, the method comprises: 
     ( 401 ) receiving, from a second communication device, a discovery or D2D message at Layer 1; 
     ( 402 ) identifying message format of the received message; and 
     ( 403 ) transmitting/sending decoded message to higher layers. 
     As previously described in conjunction with  FIG. 2 , identifying of the message may be performed before decoding of the received message, alternatively, the received message is decoded before the format of the message is identified as described above in conjunction with  FIG. 3 . 
     Referring  FIG. 5  there is illustrated main steps performed by a second communication device according to embodiments herein. As shown, the method comprises: 
     ( 501 ) obtaining, from higher layer(s) of the second communication device, a discovery or D2D message at Layer 1 for physical layer processing; 
     ( 502 ) indicating, by higher layer(s), a format of the discovery message to Layer 1; 
     ( 503 ) Encoding the obtained message according to the indicated message format; 
     ( 504 ) transmitting the encoded message to a first communication device. 
     According to an exemplary embodiment, the second communication device may use different reference signal sequences for different message formats enabling the first communication device to map the message format with a reference signal sequence as previously described, thereby identifying the message format transmitted by the second communication device. The reference signal sequence being associated with the transmitted discovery or D2D message. 
     According to another exemplary embodiment, the second communication device may use different resource mapping schemes; scrambling schemes, guard period/subcarrier or cyclic prefix (CP) or CRC for different message formats as previously described. 
     As previously described, the message formats may comprise formats such as a public safety format, a non-public safety (i.e. commercial) format and a relay message format. All these message formats may be viewed as D2D message formats or discovery D2D message formats. The format of a discovery or D2D message may be understood as a payload format of the discovery (D2D) message, which may be different for a public safety format a non-public safety format, and a relay format. The public safety format may correspond to a first payload format, and the non-public safety format may correspond to a second payload format. 
     To perform the method actions described above in relation to  FIGS. 2, 3 and 4 , the first communication device e.g. wireless device  131  in  FIG. 1  comprises the following arrangement depicted in  FIG. 6 , and as described below. The first communication device  600  comprises a processing circuit or a processing module or a processor or means  610 , antenna circuitry (not shown); a receiver circuit or receiver module  620 ; a transmitter circuit or transmitter circuit  630 ; a memory module  640  and a transceiver circuit or transceiver module  650  which may include the transmitter circuit  630  and the receiver circuit  620 . 
     The first communication device may be a wireless device e.g. a mobile terminal, wireless terminal, mobile station, mobile telephone, cellular telephone, smart phone or a device-to-device (D2D) capable UE which may operate as a relay D2D device for other D2D devices. Further examples of different wireless devices comprise laptops with wireless capability, Laptop Embedded Equipment (LEE), Laptop Mounted Equipment (LME), USB dongles, Customer Premises Equipment (CPE), modems, Personal Digital Assistants (PDA), or tablet computers, sometimes referred to as a surf plates with wireless capability or simply, tablets, Machine-to-Machine (M2M) capable devices or UEs, Machine Type Communication (MTC) devices such as sensors, e.g., a sensor equipped with UE, just to mention some examples. 
     The processing module/circuit  610  includes a processor, microprocessor, an application specific integrated circuit (ASIC), field programmable gate array (FPGA), or the like. Processor  610  controls the operation of the first communication device  600  and its components. Memory (circuit or module)  640  includes a random access memory (RAM), a read only memory (ROM), and/or another type of memory to store data and instructions that may be used by processor  610 . The first communication device  600  may comprise additional components not shown in  FIG. 6 . 
     The receiver module/circuit  620  or the transceiver module/circuit  650  is configured to receive at Layer 1 of the first communication device  600 , a discovery or D2D message transmitted from a second communication device. The processing circuit/module  610  is configured to identify a message format of the received discovery or D2D message. The processing circuit/module  610  is further configured to provide or sent decoded discovery of D2D message to higher (or upper) layer(s). According to an example, the decoded message transmitted to upper layer(s) may include an indication of the identified message format enabling the higher layer(s) of the first communication device to identity the message format. Example of discovery or D2D message formats may include a format for a relay discovery announcement; a format for a relay discovery request; a format for a discovery public safety message or a format for a discovery consumer related message. 
     According to an exemplary embodiment, the processing circuit or a processing module or processor or means  610  is configured to identify the message format before decoding the received message. Hence, according to another aspect of embodiments herein, the first communication device  600  is configured to: after identification of the message format of the discovery or D2D message received at Layer 1 from the second communication device/apparatus; decode, by means of the processing circuit or a processing module or processor or means  610 , the received discovery or D2D message according to the identified message format followed by transmitting, by means of the processor  610 , the decoded message to upper layers. As mentioned above, the decoded message to upper layers may include an indication of the identified message format enabling the higher layers of the first communication device to identity the message format. 
     According to an exemplary embodiment, the processing circuit or a processing module or a processor or means  610  is configured to identify the message format after decoding of the received message by means of the processing circuit or processing module or processor or means  610 . Hence, according to another aspect of embodiments herein, the first communication device  600  is configured, by means of the processing circuit or processing module or processor or means  610 , to decode the received message; identify the message format of the decoded discovery or D2D message and transmit the decoded message to upper layers. As mentioned above, the decoded message to upper layers may include an indication of the identified message format enabling the higher layers of the first communication device to identity the message format. Additional operations performed by the first communication device ( 600 ) have already been described e.g. 
     The memory module  640  may contain instructions executable by the processor  610  whereby the first communication device  600  is operative to perform the previously described method steps. There is also provided a computer program comprising computer readable code means which when run in the first communication device  600  e.g. by means of the processor  610  causes the first communication device  600  to perform the above described method steps as disclosed in relation to  FIGS. 2-4 , which at least include: receiving, from a second communication device, a discover or D2D message at Layer 1 of the first communication device  600 ; identifying a message format of the received message; decoding the received message according to the identified message format; and sending/transmitting the decoded message to higher layers (L2/L3) of the first communication device  600 . As previously described, the decoding may be performed before identification of the message format. 
     Additional operations performed by the first communication device  600  have already been described. 
     For example, identification of the message format may be performed by mapping the message format to at least one reference signal sequence associated with the received discovery message. For example, the first communication device  600  may detect one or more parameters associated to one or several reference signal sequences and from such parameters determine the message format of the received discovery message. 
     For example, the first communication device may be pre-configured with at least one reference signal sequence and the mapping may be performed based on the reference signal sequence. For example, sequence  1  for message format  1 , sequence  2  for message format  2 , sequence  3  for message format  3 , etc. A sequence maybe a base sequence, a group sequence, a sequence identity, a scrambling sequence, a cyclic shift, an orthogonal cover code etc. It should be noted that identification may be performed during channel estimation. In this way, by correlating the received reference signal/message to different hypothesis (e.g. with sequence  1 , sequence  2  and/or sequence  3 ), the first communication device may know which format the received message uses. For example, if a relay announcement message received by the first communication device uses a distinguishable scrambling sequence, the first communication device may identify the received relay announcement message by associating it with the distinguishable scrambling sequence. 
     According to another exemplary embodiment, identification of the message format may be performed via a resource mapping scheme by mapping between resource mapping schemes of the discovery message and the associated message format. For example, mapping scheme  1  for message format  1 ; mapping scheme  2  for message format  2 , mapping scheme for message format  3  etc. An example of a mapping scheme may be a resource location of the message. For example, the messages of different formats may be located at different time/frequency locations in a subframe carrying the message. For example, a PS message may be located at resource pool  1 ; a commercial message may be located at resource pool  2  and a relay announcement message may be location at resource pool  3 . The resource pools may be mutually orthogonal to each other. Thus, depending on the resource location where the first communication device detects a certain discovery message, the message format is identified or obtained. 
     Another example of a mapping scheme may be guard period/subcarrier location. For example, the first communication device may identify the message format depending on the location of the guard period/subcarrier in the received discovery message as well as the length of the guard period/subcarrier. For example, in a resource unit comprising X subcarriers and Y symbols, where X and Y are design parameters, a guard period (in time) or guard band (in frequency) may be defined. The first communication device may identify the format of the received message including the guard time or guard period by e.g. determining the length of the guard period at the end of the message and then identify the format type. For example, the length of the guard period or guard band may be specific to the type of message received. 
     Another example of a mapping scheme is to make use of different cyclic prefix (CP) length for the identification. For example, different message formats may be associated to different CP lengths. As an example, a message format with a predefined length K may be identified as belonging to a PS message; a message format with a predefined length N may be identified as belonging to a commercial message; a message format with a predefined length M may be identified as belonging to relay message. K, N and M are design parameters or may be defined in a 3GPP standard specification. The operations above may be performed by the processor  610  of the first communication device. 
     In another exemplary embodiment, the second communication device/apparatus may provide the first communication device with information on the used message format by means of a dedicated signalling field that may be multiplexed with the discovery message that is received by the first communication device. 
     Referring to  FIG. 7 , there is illustrated a block diagram illustrating embodiments of a second communication device  700  comprises a processing circuit or a processing module or a processor or means  710 , antenna circuitry (not shown); a receiver circuit or receiver module  720 ; a transmitter circuit or transmitter circuit  730 ; a memory module  740  and a transceiver circuit or transceiver module  750  which may include the transmitter circuit  730  and the receiver circuit  720 . 
     The second communication device  700  may be a wireless device e.g. a mobile terminal, wireless terminal, mobile station, mobile telephone, cellular telephone, smart phone or a device-to-device (D2D) capable UE which may operate as a relay D2D device for other D2D devices. Further examples of different wireless devices comprise laptops with wireless capability, Laptop Embedded Equipment (LEE), Laptop Mounted Equipment (LME), USB dongles, Customer Premises Equipment (CPE), modems, Personal Digital Assistants (PDA), or tablet computers, sometimes referred to as a surf plates with wireless capability or simply, tablets, Machine-to-Machine (M2M) capable devices or UEs, Machine Type Communication (MTC) devices such as sensors, e.g., a sensor equipped with UE, just to mention some examples. 
     The processing module/circuit  710  includes a processor, microprocessor, an application specific integrated circuit (ASIC), field programmable gate array (FPGA), or the like. Processor  710  controls the operation of the first communication device  600  and its components. Memory (circuit or module)  740  includes a random access memory (RAM), a read only memory (ROM), and/or another type of memory to store data and instructions that may be used by processor  710 . The second communication device  700  may comprise additional components not shown in  FIG. 7 . 
     The processing module/circuit  710  or processor is configured to obtain from higher layer(s) of the firs communication device, a discovery or D2D message at Layer 1 of the second communication device  700  for physical layer processing; The processing module/circuit or processor  710  is further configured to indicate, by higher layer(s), a format of the discovery message to Layer 1; and to encoding the obtained message according to the indicated message format. The transmitter circuit/module  730  is configured to transmit/send the encoded message to the first communication device  600 . 
     According to an exemplary embodiment, the second communication device  700  may use different reference signal sequences for different message formats enabling the first communication device to map the message format with a reference signal sequence as previously described, thereby identifying the message format transmitted by the second communication device. The reference signal sequence being associated with the transmitted discovery or D2D message. 
     According to another exemplary embodiment, the second communication device  700  or processor of the second communication device may use different resource mapping schemes; scrambling schemes, guard period/subcarrier or cyclic prefix (CP) or CRC for different message formats as previously described. 
     As previously described, the message formats may comprise formats such as a public safety format, a non-public safety (i.e. commercial) format and a relay message format. All these message formats may be viewed as D2D message formats or discovery D2D message formats. The format of a discovery or D2D message may be understood as a payload format of the discovery (D2D) message, which may be different for a public safety format a non-public safety format, and a relay format. The public safety format may correspond to a first payload format, and the non-public safety format may correspond to a second payload format. 
     The memory module  740  may contain instructions executable by the processor  710  whereby the second communication device  700  is operative to perform the previously described method steps. There is also provided a computer program comprising computer readable code means which when run in the second communication device  700  e.g. by means of the processor  710  causes the second communication device  700  to perform the above described method steps as disclosed in relation to  FIG. 5 , which at least include: obtaining, from higher layer(s) of the second communication device  700 , a discovery or D2D message at Layer 1 for physical layer processing; indicating, by higher layer(s), a format of the discovery message to Layer 1; encoding the obtained message according to the indicated message format; and transmitting the encoded message to the first communication device  600 . Additional operations performed by the second communication device have already been described and are not unnecessarily repeated. 
     Throughout this disclosure, the word “comprise” or “comprising” has been used in a non-limiting sense, i.e. meaning “consist at least of”. Although specific terms may be employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation. In particular, it should be noted that although terminology from 3GPP LTE has been used in this disclosure to exemplify the invention, this should not be seen as limiting the scope of the invention to only the aforementioned system. Other wireless systems, including LTE-A (or LTE-Advanced), UMTS, WiMax, and WLAN employing D2D communications may also benefit from exploiting the ideas covered within this disclosure.