The Design of TMA Gain Adjustment Based on AISG2.0

Transcription

1 The Design of TMA Gain Adjustment Based on AISG2.0 Manjunath H A PG Student, R. V. College of Engineering, Bengaluru , VTU Belagavi, India Chethana G Assistant Professor, R. V. College of Engineering, Bengaluru , VTU Belagavi, India Suma S Associate Professor, R. V. College of Engineering, Bengaluru , VTU Belagavi, India ABSTRACT This paper relates to the mobile communication, more interrelated to the gain adjustment method of Tower Mounted Amplifier (TMA), Implementation of TMA application (TMAAPP) based on the standard technical specification of 3GPP and AISG2.0 protocol, The method of communication between base station (BST) and Tower Mounted Device (TMD), software realization, gain message handling is discussed and implemented steps to handle Time consuming procedure (TCP) in parallel. Discussed work of physical, datalink, and application layer from multi-layer architecture and objectoriented scheme based on AISG2.0 communication, the TMA application has added rewards to maintain Antenna Line Devices (ALD). Keywords: AISG, RCS -RET Control System, RET -Remote Electrical Tilt, TMA. 1. INTRODUCTION The Mobile network providers face the difficulties to maintain the coverage, ability of the cell sites, the quality of communication, and the operation cost. Increase in the mobile traffic, need adjustment of Antenna Line Devices (ALDs) very frequently. Hence the keyword is flexibility. Technician has to visit the location and adjust the antenna tilt. When it is difficult to get the availability of technician, ideal environment, the special equipment s such as cranes, and access to the location of the tower. In such operations network availability will be down, which generates more complains. Antenna Interface Standard Group provided AISG2.0 protocol stack based on 3 layer OSI model, which provide easy design and remote access to the ALDs. AISG2.0 protocol stack used in application of TMA and RET. A Tower Mounted Amplifier (TMA) is a located between base station and antenna, TMA is Low-noise amplifier (LNA) used to reduces the noise figure (NF) of signal in mobile Transreceiver station which, Moreover improvement in the overall sensitivity enables BTS to receive weaker signals. A TMA adjust the gain loss seen in received signals because of long way running radio feedback cables. The TMA is used where BST and Antennae are at more distance apart. 2. TMA TOPOLOGY TMA system has dual parts, one is primary controller system and second is secondary controller. Base station is primary controller and connected to TMA device with RF feeder cable. 339 Figure 1 TMA Topology

2 OOK modulator and demodulator is used to avoid extra routing of RS485 cable. Topology is presented in Figure TMA IDENTIFICATION AND CONNECTION. TMA starts with No Address state and reply with vendor id, product number, when primary controller broadcast the XID frames. These frames are used to scan connected device and for address authentication. Figure 2 TMA State Model TMA goes to Address Assigned state after the address assignment. In the state of Address Assigned, device receives SNRM frames which converts device sate to Connected. TMA issues and handle TMA commands such as Set Gain, Get Gain commands, Set TMA mode commands from primary controller. TMA disconnect from connected state and coverts to No Address state only after issuing DISC frames. TMA device identification state model demonstrated in Figure SOFTWARE ARCHITECTURE The communication between TMA and Primary controller follows Master-slave configuration. TMA independently will not send any messages, act as slave so only respond to the primary controller messages. Primary controller has more control over bus communication. Information exchange between devices is designed using Open System Interconnect Reference Model (OSI Model), which is developed by AISG. The software architecture is represented as in Figure 3. Figure 3 Software Architecture LAYER-7: The application for Gain adjustment is developed in Application layer 7 of AISG protocol and it called TMA application (TMAAP). Application layer has the function to handle elementary procedure and give callback to TMA functions. Send response to Primary controller over layer L2. LAYER-2: Data link layer packet is part of HDLC frame and implemented based on 3GPP standard, 340

3 Layer 2 has functions to handle frames coming from layer L-1 such as UART port 0 to port 1, functions to pack, unpack HDLC frames for L7, L1 respectively. Packet queuing mechanism depend on Layer-1, Layer-7 implementation. Gives full duplex communication with L7 but send packets to L1 only on primary controller request. LAYER-1: Layer-1 is physical layer provides functions to handle sending and receiving from primary controller, Functions for modem initialization, handle I2C, SPI, and UART initialization. Physical layer designed under 3GPP standard. 5. MESSAGE COMMUNICATION BETWEEN TMA AND PRIMARY CONTROLLER 5.1 HDLC Frame HDLC frames are used by primary controller and TMA for communication. HDLC frames start with Head Flag (0x7E) and end with Tail Flag (0x7E), each field of 8-bit. Byte 2 is device address and will be addressed with 0xFF, 0x00 for broadcast messages. CTRL field to indicate type of frame such as XID, DISC, I, RR, UA, SNRM frames. INFO field has N bytes of data and CRC is 16 bit, which will be calculated for field till INFO except Head Flag and Tail Flag. Structure of HDLC frame is described in Table 1. Table 1 HDLC Frame HDLC Frame Tail Head Flag 0xFF CTRL INFO.. CRC Flag 5.2 XID Frame XID Frames are broadcast messages from Primary controller and get response message from TMA. These responses will be having TMA device info such as vendor id, product number. Primary controller assign unique address to the TMA which sent response. XID frames are identified with CTRL byte 0xBF. Table 2 XID Frame HDLC Frame Head 0xFF CTRL INFO.. CRC Tail Flag Flag XID Frame FI GI GL PI PL PV XID frame has information of device with format identifier (FI), Global Length (GL), Global Identifier (GI), Parameter Identifier (PI), and Parameter Value (PV). XID frames are packed with HDLC Frame in layer-2 then transmitted to TMA using layer-1 as shown in Table I Frame After the connection established with device TMA, I-frames are sent to adjust the Gain of TMA from primary controller. Two class of I frames are used in AISG2.0, one with response expected and other without response. TMA execute elementary procedure then send response OK, in case of unsuccessful execution send response FAIL with ERROR CODE followed in next byte. I frames are elementary procedure (EP) which are handled in application and packed with ADDR assigned in HDLC frame before sending to TMA device. Typical I-FRAME with HDLC is shown in Table 3. Table 3 I Frame HDLC Frame Head Flag ADR CTRL INFO.. CRC Tail Flag I Frame Procedure ID Data Length Data.. 341

4 Procedure ID is Elementary Procedure to be executed on device TMA, Data length is 16 bit number which is followed by Data of length N. I-Frame sent from TMA has message <OK> for successful execution and <FAIL> for un-successful execution with <ERROR CODE> in next byte. CRC is calculated before sending. 6. DESIGN FLOW CHART AND COMMANDS Software design made easy to understand with layered architecture. The layer L1 (Physical layer) provide function to handle peripheral drivers, which is responsible for initialization, Interrupt handling, message queuing, and process the HDLC frame to the above Layer L2 (Datalink layer). Layer L2 responsible for connection establishment and packing-unpacking of HDLC frame, which transfer only INFO to the above API. Data Link Layer 2 handles XID frames to provide connection establishment. Figure 4 Message Communication with TMA Layer L7 (Application layer) handles user APIs and provide callback functions for handling ALDs such as TMA, RET devices. Application layer responsible for TMA initialization and gain settings. Layer L7 provide abstracted virtual layer for user interface, which allows to handle elementary procedure in easier and robust way to provide apparent link with TMA device. The graphical representation of Layered architecture is given in Figure 4. Tower Mounted Amplifier (TMAAP) application concentrate more on gain settings and clearly defined querying and setting the TMA Gain interface based on AISG protocol. Functions for TMA gain interface are listed in Table 4. Table 4 TMA Commands TMA Specific Commands Command Command Number Set TMA Mode 0x40 Get TMA Mode 0x41 Set TMA Gain 0x42 Get TMA Gain 0x43 Get Device Data 0x0F Prior to the gain setting, primary controller should know the range of Gain supported by connected TMA device. TMA device data queried with command Get Device Data. The list of parameter for TMA device is listed in Table VI-2. Message format for query Get Device data is as follows: I Frame: <0x0F><Length Byte><0x01><0x02>. <0x0N> Failure response message where TMA not support Get Device command is as follows: 342

5 I Frame: <0x0F> <Length Byte> <FAIL> <Error code 1> <Error Code N> The response message from TMA with device parameter is as follows: I Frame: <0x0F> <Length Byte> <OK> <Parameter 1> <Parameter N> From above response message, primary controller get to know the gain adjustment supported by the connected TMA. If resolution in Table 6 is zero then TMA does not support linear gain adjustment and Primary controller send non-linear gain value 3dB, 6dB, 12dB, and 24dB depend on the command response received, which enables the TMA maintainability and thereby increase the network quality. Table 5 TMA Device Parameters Field No Length (Bytes) Format Description 0x11 15 ASCII Model Number 0x12 17 ASCII Serial Number 0x13 1 unsigned TMA Type 0x14 4 unsigned Rx Frequency Band 0x15 4 unsigned Tx Frequency Band 0x16 1 unsigned Max Gain (db/4) 0x17 1 unsigned Min Gain (db/4) 0x18 1 unsigned Gain Resolution (db/4) Gain adjustment is different for each TMA devices. The software flow of TMA Gain adjustment is explained in Figure 5. Figure 5 TMA Gain Adjustment Flow Chart After the query of gain type. When the TMA is gain adjustable, primary controller set the TMA to bypass or normal mode with Set TMA Mode command. TMA works on default gain in mode of bypass. TMA gain can be adjusted with Set TMA Gain command based on TMA Gain adjustment type either in linear or nonlinear step. 7. PRIMARY CONTROLLER GUI INTERFACE Many companies of primary controller provider entered the field of telecommunication such as Kathrein, KMW, RFS system, and Kathrein PCA Controller. The Implemented software for TMA gain adjustment on secondary device is validated using Kathrein primary controller. Graphical User interface (GUI) of Kathrein for Antenna Management system can be accessed using given static IP address. After scanning the connected TMA, GUI displays the TMA device parameter 343

6 and User interface for gain adjustment as presented in Figure 6. Figure 6 Kathrein Primary Controller GUI In the given GUI 6, Get info button send command Get Info and receive response packet with TMA device vendor Id, Product Number. Set TMA Mode under main menu sub unit 1 is used to set TMA gain type, bypass TMA mode allows TMA to work with default gain. When connected TMA mode does not support either linear or nonlinear adjustment, Set TMA Gain button will not be enabled. 8. SUMMARY The conclusion of the paper is, with large increment in the number of network operators, network interference, issue of weaker signals, cable over length with Base Station, and Noise figure (NF). TMA is very much essential in communication, to boost gain in case of weaker signal and bypass the gain adjustment when received signal with high gain. The software intended for TMA gain adjustment enables network operator for easy control and monitor of the tower mounted amplifier gain. Primary controllers provided added feature to monitor the status over the Ethernet. This implementation increase the revenue for mobile network providers with good quality calls and internet browsing with less base station and from there saving in the cost. REFERENCES [1] Weidong Sun, A TMA Gain Adjusting Method system European Patent EP A2, issue date Apr [2] Antenna Line Device Configuration System publication no W A1, March [3] João Moreira Rebelo, The Need For TMA Amplifier available online. [4] AISG Version 2.0, Control Interface for Antenna Line Devices [ [5] 3GPP TS25.460, UTRAN Iuant Interface General Aspects and Principles Release 6. [6] Li Wensheng, The Design of RET Control System Based on AISG2.0 ieee explore