Application Experiment Ground Station Guidelines

Transcription

1 Application Experiment Ground Station Guidelines November 27, 2006

2 Introduction These "Application Experiment Ground Station Guidelines" provide information on the requirements of the earth station equipment for WINDS and may help in the preparation of experiment proposals. [Note] ABOUT UPDATES TO THIS PAPER Some of the WINDS specifications are presented here as a reference only, and are subject to change as the WINDS design matures in the future. Any updates will be incorporated as necessary. i

3 Table of contents 1. Outline of WINDS 1 2. Network configuration using WINDS ATM baseband switching mode Bent-pipe TDMA mode 3 3. Terminal types and examples of link budget Types of user terminals Examples of link budget 6 4. Hardware requirement of user terminal Functions of user terminal Performance of RF equipment Performance of baseband equipment [TBD] * 5. Outline of protocols ATM baseband switching mode Bent-pipe TDMA mode [TBD] * 6. Additional information Examples of improvement of TCP performance Issues of international frequency coordination Requirements for common frequency usage with Fixed Wireless Access (FWA) systems Example of development of prototype earth station 22 [Terminology] 24 * To be added in the revised edition. ii

4 1. Outline of WINDS WINDS (Wideband InterNetworking engineering test and Demonstration Satellite) is an experimental satellite enables communications at significantly higher data rates. The satellite employs very advanced technologies described below in order to realize both very high data rate transmissions and advanced broadband satellite networking. 1) Fixed multi-beam antenna (MBA) and Ka-band multi-port amplifier (MPA) Japan and several areas in Southeast Asia are covered by MBA spot-beams. The MBA can generate a narrow beam width (spot beam) to concentrate the energy of the transmitted and received radio wave, and provide a required functions for high data rate satellite communications. The MPA, used with MBA, amplifies the transmitting power of several channels (maximum 8ch) simultaneously, and can allocate power for each channel arbitrarily. For the Ka band, it enables the allocation of power to areas specified in the experiment plan to compensate for a significant attenuation that may be caused by rainfall. 2) Ka-band active-phased array antenna (APAA) The APAA antenna can steer beams electronically within +/-7 degrees in the north-south direction or +/-8 degrees in the east-west direction from the sub-satellite point with a beam, and generate two beams simultaneously. Areas not covered by MBA can access WINDS using the APAA. The performance (EIRP, G/T) of the APAA is less than that of the MBA, so larger earth stations are required for APAA access than for MBA access. 3) Onboard Switching Router(ABS : ATM Baseband Switch) The ABS receives the data bursts sent by users, demodulates them, redirects them by destination address attached in a header of the ATM cell, and transmits them to the destination user. Because the ATM cells to be sent to the same beam are multiplexed in a downlink, the transmission power of the satellite transponder can be used efficiently and layer 2 routing is performed at the same time. 4) Very Wide Bandwidth Transponder The ABS can be bypassed in the WINDS transponder, which is called the "Bent-pipe TDMA Mode". In this case, the full bandwidth transponder of 1.1GHz can be utilized. The users' data bursts are not be demodulated onboard, but satellite switching can be performed by switching the IF-Switch in satellite switched time division multiple access manner. (SS-TDMA) Due to the advanced technologies described above, WINDS provides superb communications capability in a variety of networking configurations, such as: - Mesh type networking connecting many sites at high data rates (max Mbps) and carrying multimedia contents. - Mesh or star type networking connecting several sites at very high data rates (1.2Gbps). 1

5 * Remarks Although WINDS provides very high data transmission rates, high throughput is not achieved in some cases of Internet use. It degrades Transmission Control Protocol (TCP) performance, but the degradation can be avoided by using TCP extension or Performance Enhancing Proxy (PEP) technology. Information regarding this issue is described in section 6.1 (2). 2. Network Configuration with WINDS 2.1 ATM baseband switching mode Topology of connection Figure.2-1 shows the connection topology in when the ATM baseband switching mode is used. Here, each user terminal is logically connected to the ABS onboard the WINDS. The ABS demodulates signals from user terminals, identifies the header of cells, and transfers association cells and traffic data cells to the Network Management Center (NMC) and to destination user terminals, respectively. When user stations communicate with one another, first they are given an assignment of time slots on a traffic link (data link) between them by means of a signaling link, and then transfer data between them on the assigned time slots. The signaling slot is pre-assigned for area, so the user terminal should use the assigned slot in the area where the terminal is located. The association data must employ ATM layer protocol which the ABS can treat, and SAAL protocol which the NMC employs. Traffic data should be formatted as ATM cells which the ABS can treat, but upper layer protocols are not specified by the WINDS network itself Information transmission capacity In the ATM baseband switching mode, the information transmission capacity depends on the performance of an ABS modulator/demodulator installed in WINDS, the transmission/reception performance of a transponder in WINDS, and the transmission/reception performance of an earth station. In the case of communication within Japan, the scale of an earth station to accommodate the maximum information transmission rates of an uplink and a downlink will be described below: a) Uplink 1.5 / 6 Mbps: Compact small terminal which can be installed at home (USAT) 24 / 51 Mbps: VSAT which can be installed in schools and SOHOs (1~2mø:HDR-VSAT), or larger terminals (2~3mø: SDR-VSAT, 5mø:LET) 155 Mbps: HDR-VSAT, SDR-VSAT or LET which can transmit three 51 Mbps signals. b) Downlink 155 Mbps: All user terminals described in the uplink section. 2

6 WINDS ABS Traffic link Signaling link External network ODU IDU Router Connecting to other AS NMC TDMA slot assignment and other link control (NMC: Network Management Center) ODU IDU Terminal User in the WINDS network Figure.2-1 Topology of connection in the ATM baseband switching mode 2.2 Bent-pipe TDMA mode The bent-pipe mode enables TDMA or CW (continuous-wave) operations. The topology of connection and the information transmission capacity by means of TDMA will be described below: Topology of connection Fig.2-2 shows the topology of connection in the bent-pipe mode. Each user terminal connects to the destination user terminals through WINDS in this mode. In this mode, unlike the ATM baseband switching mode, the physical link (time slot) is assigned by the pre-assignment system by which each user station is given an assignment of time slots used for data transmission in advance in the planning stage of experiment. Each user station acquires information on its slot assignment and timing of transmission/reception by receiving and demodulating notifications distributed from the NMC via WINDS Information transmission capacity Data transmission capacity in this mode depends on the performance of the WINDS transponder and the performance of earth terminals. The WINDS project aims at realizing higher data rates via satellite than existing satellite communications systems. Therefore, 622Mbps is a basic transmission rate in the WINDS network in the bent-pipe mode, and is achieved when a physical link is established by one earth terminal. Double linking achieves transmission rate of 1.2Gbps. 3

7 (The technical challenge of achieving 1.2Gbps with single channel is now under study.) The information necessary for setting a link is distributed as a notification to each user at a transmission rate of 155Mbps. It is necessary to demodulate the notification information for TDMA communication by means of the bent-pipe mode. To achieve the above-mentioned transmission rate, basically an earth station (SDR-VSAT or LET) of a scale of at least 2-3mø is necessary within Japan. WINDS SW Matrix Traffic link Signaling link External network ODU IDU Router Connecting to another AS NMC TDMA slot assignment and another link control (NMC: Network Management Center) ODU IDU Terminal User in the WINDS network Figure. 2-2 Topology of connection in the bent-pipe TDMA mode 4

8 3. Terminal types and examples of link budget 3.1 Types of user terminals The following table shows specified user terminal types for WINDS experiments. Type USAT HDR-VSAT SDR-VSAT LET Description Mini earth station that can be installed home Small earth station that can be installed in schools, SOHO, etc. Medium size terminal for corporate use Large scale terminal for installation in large enterprises and research organizations. Table 3-1 User terminal types for WINDS experiments Applicable operation mode ATM baseband switching ATM baseband switching ATM baseband switching Maximum information rate in uplink *1 Maximum information rate in downlink MBA1 MBA2 *2 APAA *3 1.5/6Mbps 155Mbps 1.5/6/24/51/ 155(51 x 3ch)Mbps *4 1.5/6/24/51Mbps 155(51 x 3ch)Mbps *4 155Mbps 155Mbps Bent-pipe 622Mbps 622Mbps ATM baseband switching Bent-pipe 1.5/6/24/51Mbps 155(51 x 3ch)Mbps *4 622Mbps 1.2Gbps(622M x 2ch) 155 Mbps 622Mbps 1.2Gbps (622M x 2ch) : This can be used subject to conditions. *1 In the case of ATM baseband switching, 1.5Mbps is needed for a signaling link, and, for a traffic link, any one of 1.5, 6, 24, 51 and 51 x 3 Mbps is used. *2 Assumed link availability is 98 %. Higher link availability requires a higher EIRP and G/T for the user terminal. *3 Because APAA's EIRP and G/T are smaller than those of MBAs, the G/T and EIRP of the user terminal should have a larger than those of MBAs. In addition, the required EIRP and G/T differ slightly by area and location of earth terminal. *4 155Mbps (Uplink) requires 3 channels use of 51Mbps. 5

9 3.2 Examples of link budget Typical link budget calculations are shown in this section. Because rain attenuation depends on the location of the earth station, these calculations are based on a clear sky condition. When downlink rain attenuation occurs, increased noise temperature affecting the earth stations must be considered for correct calculations. 1) ATM baseband switching link for USAT in MBA1 coverage(1.5/155mbps) Area Hokkaido East Beam (Nemuro) Item unit uplink downlink Freq. GHz EIRP dbw 41.8 USAT 64.4 MBA1 Pointing Loss db Included in EIRP Free Space Loss db Polarization Loss db Absorption Loss db Rain attenuation db Pointing Loss db Included in G/T G/T db/k 17.7 MBA USAT Rx C/No db Hz Total C/No db Hz Required C/No db Hz Margin db Modulation QPSK QPSK Required Eb/No db 7.3 BER: BER: Transmission Degradation db Bit rate * db Hz Mbps Mbps Required C/No db Hz * Actual bit rate becomes larger than the information bit rate because preamble, error correction code and other redundant parts are added to the information bits to form a burst format. 6

10 2) ATM baseband switching link for HDR-VSAT in MBA1 coverage(51/155mbps) Area Hokkaido East Beam (Nemuro) Item unit uplink downlink Freq. GHz EIRP dbw 57.4* VSAT 57.5 MBA1 Pointing Loss db -0.5 Included in EIRP Free Space Loss db Polarization Loss db Absorption Loss db Rain attenuation db Pointing Loss db Included in G/T -0.5 G/T db/k 17.7 MBA VSAT Rx C/No db Hz Total C/No db Hz Required C/No db Hz Margin db Modulation QPSK QPSK Required Eb/No db 7.3 BER: BER: Transmission Degradation db Bit rate db Hz Mbps Mbps Required C/No* db Hz * In case of 51Mbps 3(=155Mbps)uplink, 4.8dB should be added. 7

11 3) ATM baseband switching link for HDR-VSAT in MBA2 coverage (51/155Mbps) Area Manila Item unit uplink downlink Freq. GHz EIRP dbw 55.7* VSAT 57.1 MBA2 Pointing Loss db -0.5 Included in EIRP Free Space Loss db Polarization Loss db Absorption Loss db Rain attenuation db Pointing Loss db Included in G/T -0.5 G/T db/k 19.0 MBA VSAT Rx C/No db Hz Total C/No db Hz Required C/No db Hz Margin db Modulation QPSK QPSK Required Eb/No db 7.3 BER: BER: Transmission Degradation db Bit rate* db Hz Mbps Mbps Required C/No* db Hz * In case of 51Mbps 3(=155Mbps)uplink, 4.8dB should be added. 8

12 4) Bent-pipe link for SDR-VSAT in MBA1 coverage (622 Mbps) Area Hokkaido East Beam (Nemuro) Item unit Uplink downlink Freq. GHz EIRP dbw 72.6 SDR-VSAT 65.2 MBA1 Power Allocation Loss db Pointing Loss db -0.5 Free Space Loss db Polarization Loss db Absorption Loss db Rain Attenuation db Pointing Loss db -0.5 G/T db/k 17.7 MBA SDR-VSAT Rx C/No db Hz Included in MBA Total C/No db Hz Required C/No db Hz Margin db 3.0 Modulation QPSK Required Eb/No db 7.3 BER:5 x 10-4 Transmission Degradation db -4.0 Bit Rate db Hz Mbps Required C/No db Hz

13 5) Bent-pipe link for LET in APAA coverage (622 Mbps) Area Sydney (1 beam operation) Item unit uplink downlink Freq. GHz EIRP dbw 80.1 LET 55.3 APAA Pointing Loss db Free Space Loss db Polarization Loss db Absorption Loss db Rain Attenuation db Pointing Loss db G/T db/k 8.7 APAA 34.1 LET Rx C/No db Hz Total C/No db Hz Required C/No db Hz Margin db 1.1 Modulation QPSK Required Eb/No db 7.3 BER: Transmission degradation db -4.0 Bit Rate db Hz Mbps Required C/No db Hz

14 4. Requirements for user terminal The following sections describe requirements for user terminals used in the WINDS experiments. 4.1 Functions of user terminal TDMA synchronization function All user terminals should have a TDMA synchronization function by receiving reference burst sent from WINDS. See section 5 for TDMA format and synchronization method Signaling functions The user terminals needs to have the function of receiving a response as information on available traffic slots to an association request by sending the request on signaling slots and receiving reference busts from the MNC to acquire traffic slots for data transmission when it starts communication. (Demand-assignment system) For the bent-pipe mode, the pre-assignment system is used where slots are assigned in advance RF signal transmission functions The user terminal should send a burst signal in a signaling slot or assigned traffic slots of assigned frequency channel in the Ka-band. For the uplink frequency for an association request, any frequency in the frequency channel assigned to a beam for the earth station should be used; and for traffic bursts, the frequency assigned in a response to an association request should be used. (Both in the 27GHz band) The earth station should have the functions of coding, modulating and transmitting an association request on signaling slots and transmission data on traffic slots. 1) Burst format See section 5. 2) Transmission scheme a) Modulation: QPSK (not specified for traffic burst in bent-pipe TDMA mode) b) Error correction: Reed-Solomon Code RS(255, 223) (not specified for traffic burst in bent-pipe TDMA mode) 3) Transmission power control function (TPC function) The user terminal should have the functions of estimating rain attenuation from the level of reception of reference burst signals transmitted from WINDS and automatically controlling the transmission power according to the estimates. For the bent-pipe mode, these functions are preferable. For the estimation of rain attenuation on downlink, signals for a Ka band telemetry link, described in 4.1.5, can be used. 11

15 4) Automatic Frequency Control (AFC) Function The user terminal should provide control of the assigned transmitting frequency RF Signal reception function The user terminal should receive, demodulate and decode reference bursts transmitted on signaling slots, and traffic burst signals for its area. It should also identify an ATM cell header in the decoded signals to extract the data addressed to it. Down link frequency is 18GHz band. 1) Burst format See section 5. 2) Transmission scheme a) Modulation: QPSK (not specified for traffic burst in bent-pipe TDMA mode) b) Error correction: Reed-Solomon Code RS(255, 223) (not specified for traffic burst in bent-pipe TDMA mode) Satellite tracking function (this applies only to SDR-VSAT and LET) The earth station should be capable of tracking the WINDS satellite by using the residual carrier of signals for a Ka band telemetry link transmitted from the satellite. (The Ka band telemetry link is a separate link provided for the monitoring of the state of mission equipment onboard satellite.) The specifications for signals for the Ka band telemetry link (downlink) are as follows. a) Frequency: 18.9GHz band b) Transmission EIRP: 17.2dBW (θ < 6deg.), 15.7dBW (θ < 8deg.) *θ is an angle of the earth station to the subsatellite point as zero degree (a half of the vertex angle at the satellite). c) Polarization: RHCP d) Modulation: PCM (NRZ-L)/PSK/PM e) Sub-carrier frequency: 40 KHz f) Modulation depth : 1.1rad ± 10% or less g) Data rate of information: 10kbps Base-band interface function The user terminal needs to have a base-band interface with the equipment, such as data terminals and routers, that the user uses. This function depends on the equipment that the user uses, so the user is required to confirm the specifications and performance by itself. 12

16 4.2 Specifications of RF equipment Table 4-1 shows the specifications of the RF part of the earth station. Fig. 4-1 shows the transmission and reception frequencies (provisionally specified). UPLINK BCN PIL 28.8 Ka telecommand NIL MHz MHz MHz 74 MHz MHz MHz 74 MHz MHz MHz MHz 275MHz 270MHz 1.5Mbps Mbps 再生中継回線 ATM baseband switching link 6, 6 24 or 51Mbps Mbps 再生中継回線 ATM baseband switching link 155Mbps Mbps 再生中継回線 ATM baseband switching link MHz MHz MHz MHz 622Mbps Mbps 非再生中継回線 bent-pipe TDMA link DOWNLINK Ka telemetry NIL MHz 185 MHz 185 MHz MHz 270 MHz Figure. 4-1 Transmission/reception frequencies (provisionally specified) 13

17 Table 4-1 Specifications of RF User Terminal Equipment USAT HDR-VSAT SDR-VSAT LET Transmitting frequency 27GHz band (tentative) Stability of transmitting frequency Receiving frequency 18GHz band (tentative) EIRP (linear operation) 48.8dBW * dBW * dBW 80.2dBW G/T 11.5dB/K 19.0dB/K 24.5dB/K 32.0dB/K Dynamic range of receiving signal 10.0dB 10.0dB TBD TBD Polarization Vertical or Horizontal (Linear) Separation of polarization 20dB 25dB TBD TBD Side lobe To meet ITU-Rrec. S580-5 Off-axis emission To meet ITU-Rrec. S524-8 RF frequency-amplitude characteristics TX: ±0.7dB/6.4MHz TX: ±1.0dB/51.8MHz 0.75dB/500MHz 0.75dB/500MHz RF frequency-phase characteristics TX: ±0.1dB/6.4MHz TX: ±0.2dB/51.8MHz 1nsec/300MHz 1nsec/300MHz RF phase noise characteristics TX: 3deg.rms TX: 3deg.rms -60 dbc at 1kHz from center frequency (less than 20kHz-4.6MHz) (less than 20kHz-37MHz) -70 dbc at 10 khz from center * 1: In the case of up-link maximum information transmission rates (6Mbps), * 2: In the case of up-link maximum information transmission rates (51x3Mbps) [Attention] ITU-R specifies off-axis emission power density of earth station in order to avoid interference between satellite networks. User terminal should reflect this recommendation, especially the antenna diameter is very small. Refer to the attached information on ITU-R recommendations regarding off-axis EIRP of earth station (S.524-8) 14

18 Excerpts of RECOMMENDATION ITU-R S Recommends 4-That earth stations operating in GSO networks in the FSS operating in the GHz frequency band be designed in such a manner that at any angle, ϕ, which is 2 or more off the main lobe axis of an earth station antenna, the e.i.r.p. density in any direction within 3 of the GSO should not exceed the following values: Angle off-axis Maximum e.i.r.p. per 40 khz 2 ϕ 7 (19 25 log ϕ) db(w/40 khz) 0 7 < ϕ db (W/40 khz) < ϕ 48 (22 25 log ϕ) db(w/40 khz) 48 < ϕ db (W/40 khz). For any direction in the region outside 3 of the GSO, the above limits may be exceeded by no more than 3 db; NOTE 21 In the frequency range GHz for earth stations whose antenna diameter is less than 65 cm, the off-axis e.i.r.p. density levels given in recommends 4 may be exceeded by up to 3 db provided that the maximum off-axis e.i.r.p. density does not exceed the following values: Angle off-axis Maximum e.i.r.p. per 2 MHz 2 ϕ 7 (37 25 log ϕ 10 log M) db(w/2 MHz) 7 < ϕ 9.2 (16 10 log M) db(w/2 MHz) 9.2 < ϕ 48 (40 25 log ϕ 10 log M) db(w/2 MHz) 48 < ϕ 180 (7 10 log M) db(w/2 MHz). Where M is the number of earth stations which are in the receive beam of the satellite to which these earth stations are communicating and which are expected to transmit simultaneously in the same 2 MHz band and in the same polarization. It should be noted that for these cases a reduction in e.i.r.p. density, or additional orbital separation, would be required in order to arrive at the same adjacent satellite interference in the Earth-to-space direction as would result from the off-axis e.i.r.p., values as specified in recommends 4. 15

19 5. Outline of protocols 5.1 ATM baseband switching mode In this mode, all user terminals should be synchronized to the ABS onboard WINDS, and a user terminal can transmit signal in assigned signaling slot and assigned traffic slots. The following section outlines processing procedure Synchronization method 1) TDMA Frame In the ATM baseband switching mode, the TDMA frame structure shown in Figure is employed for all of frequency channels. The basic frame consists of 20 time slots whose duration is constantly 2msec. The first slot of the basic frame, the "Signaling Slot (SS)" is used to send the Association Request burst from users in uplink and to send the Reference Burst to provide notice of slot assignment control and ABS status in downlink. The 19 other time slots, called Traffic Slots and assigned to users according to user' requirement are used for data transmission between users. A Super Frame consists of the 16 basic frames described above. Each signaling slot in the 16 frames of a Super Frame is pre-assigned to 16 areas on the Earth. In other words, the WINDS network can provide communications services to 16 areas, and users in the 16 areas can send an association request once in a Super Frame, and then send data in the assigned Traffic Slots. Super Frame = 16 Frames (640 msec) Frame#1 Frame#2 Frame#3 Frame#4 Frame#16 Frame = 20 Slots (40 msec) SS TS#1 TS#2 TS#3 TS#4 TS#19 SS : Signaling Slot 2 msec 2 msec TS : Traffic Slot SS in Frame#n is assigned to Area#n. フレーム #nのssはエリア #nに割り当てられている. TSs in a Super Frame are assigned to user data traffic dianmically. スーパーフレーム中のTS はダイナミックにユーザ間データ転送用に割り当てられる. Figure TDMA Frame Structure (ATM baseband switching Mode) 2) Outline of synchronization The WINDS network requires that all user terminals be synchronized to the WINDS network. The Reference Burst (RB) is used to synchronize user terminals. As mentioned in the previous section, the RB is sent to define users once in a Super Frame. The first part of the RB contains a 32 bit 16

20 code (Unique Word) for timing detection, and a user terminal can detect the Super Frame using this bit sequence. Because each user terminal should know the order of the receiving RB in a Super Frame, the user terminal can determine the starting point of the receiving Super Frame. The frame timing can be obtained by dividing the Super Frame by 16. In addition, the slot timing can be obtained by dividing the Frame timing by 20. Once the receiving timing is obtained, transmitting timing can be obtained using satellite orbit information and physical allocation of the user terminal. The orbit information of the WINDS satellite is also contained in every RB. The user terminal must not be used to transmit a signal if it receives RBs. (Inter-locking function) Connection control method 1) Association burst When a user starts communication, the user terminal sends an association burst including connection request information to the signaling slot assigned to the user s area. When more than one earth station sends requests for association at the same time, there can be competition for association. So the earth station needs to be capable of retransmitting an association request after a random wait time. 2) Assignment of traffic slots The connection request from users included in the association bursts is transmitted to the network management center (NMC) in the Tsukuba Space Center via ABS. The NMC assigns traffic slots to users based on the request, current assignment status, satellite power allocation situation, and other parameters. The determined slot assignment information is delivered by RB to user terminals. The user terminal should recognize the assigned user traffic slots from the assignment information in RB, after which the user terminal is permitted to send data bursts to the destination user terminal using only the assigned traffic slots. 3) Connection termination When a user terminal ends communication with a destination user terminal, its terminal should send an Association termination request burst using ATM cell (VPI/VCI to NMC) toward the NMC. The NMC should terminate the connection based on the Association termination request, and release the assigned traffic slots for connection Burst format Figure shows the burst format. Both the association burst, RB and traffic burst employ this format which enables transmitting in the 2msec time slot. 17

21 2 msec HDR PA UW DB#1 DB#n DB#N TRL GT Uplink CR BTR CR = all 0 BTR = Info#n RS#n 32 Bytes Downlink BTR 50 Bytes BTR = Cell1 Cell2 Cell3 Cell4 Pad 223 Bytes HDR : Header ヘッダ PA : Preamble プリアンブル CR : Carrier Recovery 搬送波再生部 BTR : Bit Timing Recovery ビットタイミング再生部 UW : Unique Word ユニークワード DB #n : n-th Data Block 第 n データブロック TRL : Trailer トレイラ GT : Guard Time ガードタイム Info#n : n-th Information 第 n 情報 RS #n : n-th Reed-Solomon Code 第 nリードソロモン符号 Cell : ATM Cell Pad : Padding パディングビット Figure Burst Format A header and trailer are added to the main body of a burst in order to cancel the transient response of the circuit. The bit sequence for these parts is all "0s" for the uplink and the same sequence as BTR for the downlink. The number of data block varies according to transmission rate. Each data block consists of an information field of 223Bytes and 32Bytes Reed-Solomon code. The addition of a header, trailer, Reed-Solomon code and guard time makes the actual transmission rate higher than the information rate. The "symbol rate" is defined as the half rate of this actual transmission rate because QPSK is used as the modulation scheme. These parameters are shown in table Table Burst transmission Parameters Up / Down Information rate Nh *1 Nt *2 N *3 Symbol rate Uplink 1.5 Mbps Msps 6Mbps Msps 24Mbps Msps 51Mbps Msps Downlink 155Mbps Mbps *1 : Number of header bits,*2 : Number of trailer bits,*3 : Number of data blocks Pre-amble for uplink burst consists of 200 bits of carrier recovery (CR) and 200 bits of bit timing recovery (BTR). Pre-amble for downlink burst consists of 400 bits of BTR only. Bit sequence of these pre-amble are shown in Figure Unique words (UW) for reference burst (RB) are distinguished from other burst in order to identify 18

22 the RB, because the UW in RB is used to detect super frame timing. The bit sequence of those UWs is shown in table Table Bit Sequence of Unique Words Type of Burst I-channel Q-channel Reference Burst (0xCBC4) (0x343B) Traffic Burst (0xB706) (0x48F9) Association Burst same as traffic burst same as traffic burst 19

23 6. Additional information 6.1 Examples of improvement of TCP performance It is known that the throughput of Transport Control Protocol (TCP) is markedly degraded much over a satellite link with a long delay or a very high speed fiber optic link (so called "long fat pipe")..a few solutions, described below, have been developed to solve this problem. 1) TCP Extension The Internet Engineering Task Force (IETF) has developed TCP Extension technique to overcome the degradation of TCP throughput. This technique is opened as RFC-1323, RFC-2018 and RFC-2488, and many workstations employ these RFCs. TCP throughput can be improved by making these TCP extensions active before beginning experiments. 2) Using special protocol for satellite link The TCP extension described above, however, cannot eliminate degradation by "slow start" process or "congestion control" mechanism. To solve this issue, another technique using a different protocol dedicated to the satellite links has been developed. Here, protocol conversion between common TCP/IP and the dedicated protocol should be done at the edge of the satellite links. The equipment for protocol conversion is called "Performance Enhancing Proxy (PEP)". One such popular dedicated protocol is "express transport protocol (XTP)", and PEP using XTP is commercially available. This technique still raises a few issues however such as: - when an error occurs in satellite links, the reliability of information transmission between terminals at both ends is not guaranteed, - protocol conversion is not possible if IPSec is employed. 6.2 Issues of international frequency coordination Satellite network utilizing WINDS is under international coordination. For this purpose, earth stations listed below are submitted. Type of earth Antenna pattern Maximum Maximum transmitting stations transmitting power(dbw) power density at antenna input (dbw/hz) USAT 29-25logθ HDR-VSAT 29-25logθ SDR-VSAT 29-25logθ LET 29-25logθ Requirements for common frequency usage with Fixed Wireless Access (FWA) systems Note that care is necessary with regard to interference between the WINDS satellite network and 20

24 FWA. It is recommended that you check the laws and recommendations concerning requirements for common frequency usage with the FWA in your location. 21

25 7 Example of development of a prototype earth station Table 7-1 shows the specifications for an earth station in the experimental WINDS system that JAXA and NICT refer to as a base of design. Fig. 7-1 shows diagrams and views of USAT and VSAT under development in WINDS. Table 7-1 Baseline of Specifications of Earth Stations for WINDS Experiments USAT HDR-VSAT SDR-VSAT LET Transmission frequency range 27GHz band Receiving frequency range 18GHz band Antenna diameter 0.45m 1.2m 2.4m 5m equivalency Required G/T +11.5dB/K +19.0dB/K +24.5dB/K +32.0dB/K Required EIRP (linear operation) +48.8dBW +66.9dBW +76.0dBW +82.0dBW Polarization Linear ( V/H depends on the area where the earth station is locating) Transmission signals Data transmission (traffic), signaling Information rate Uplink: Uplink: 1.5/6Mbps (traffic) 6/24/51/155Mbps (traffic)* 1.5Mbps (signaling) 622Mbp (traffic), 155Mbps (reference burst) 1.5Mbps (signaling) Downlink: 155Mbps Downlink: 155Mbps Error correction code Reed-Solomon code RS(255,223) for traffic and signaling Traffic: N/A Reference burst: reed-solomon code RS(255,223) Modulation scheme Uplink: QPSK (burst format) Uplink: N/A Downlink: QPSK Multiple access schemes Uplink: MF-TDMA Downlink: MF-TDMA TDMA Transmission power control Required Expected installation case Transportable Transportable by vehicle (half -day installation) Transportable by vehicle Fixed model Automatic satellite tracking Not required (manual tracking by monitoring residual carrier of network monitoring signal) Required (using residual carrier of network monitoring signal) * 155Mbps (Uplink) requires 3 channels use of 51Mbps 22

26 PC etc. fixed PC etc. fixed PC etc. 全面差し替え Fig. 7-1 Configuration of USAT for WINDS developed by JAXA Figure. 7-1 Configuration of USAT for WINDS developed by JAXA 23

27 [Terminology] ABS APAA AS Association request ATM EIRP G/T HDR-VSAT IETF IF Switch IP LET MPA QPSK SAAL SDR-VSAT TCP TPC USAT WINDS Signaling slot Association request burst Uplink Area Link availability ATM Baseband Switch : high speed ATM switch on-board WINDS Active Phased Array Antenna : Electronically steerable beam antenna which has antenna array with amplifiers and phase shifters Autonomous System:An Internet unit network in independently controlled by a single administrator. Information with which the user station notifies a reference station of a connection request Asynchronous Transfer Mode:Layer-2 protocol commonly used in broadband networks. Featuring advanced QoS control or friendliness to multi-media communication. Equivalent Isotropic Radiated Power Gain to noise temperature ratio High Data Rate Very Small Aperture Terminal Internet Engineering Task Force: A group researching Internet technology to be used as standards. Onboard switch to change the path inside WINDS in down converted intermediate frequency (not regenerative) Internet Protocol Large-scale Earth Terminal Multi-Port Amplifier: An amplifier with several input and output ports. Quadrature Phase Shift Keying (modulation scheme) Signaling ATM Adaptation Layer Super high Data Rate Very Small Aperture Terminal Transport Control Protocol Transmission Power Control Ultra Small Aperture Terminal Wideband InterNetworking engineering test and Demonstration Satellite Time slot dedicated to sending association request burst or reference burst located at the first part of each TDMA frame. A burst which a user sends to the network control station (NMC) to notify it of connection request. Link from earth station to the WINDS Physical area on the earth surface covered by a WINDS antenna beam. Percentage of communication link that can be used. (time which the link suffers from rain attenuation or other reason is eliminated) 24

28 Network Management Center (NMC) Signaling Information rate Throughput Slot Cell Downlink Long fat pipe Traffic Traffic burst Traffic data Beam Protocol Baseband Header Reference burst Routing Layer 2 Signaling slot An earth station dedicated to control of the WINDS network, which it is planned will be located at the Tsukuba Space Center of JAXA. Connection control between user terminals such as connect, release, etc. Transmission rate of user information. Physical bit rate becomes larger than information rate because redundant bits such as error correction code are added to user information. Efficiency of link usage. A unit of time sliced. WINDS defines a slot as 2 msec duration. Data transmission block in ATM protocol. A cell consists of 5 Bytes (octet) of header and a 48 Bytes(octet) data field. Link from the WINDS to earth stations Communication link with a large delay-bandwidth product. Exchange of data between users. A burst which carries data between users. Information transmitted between users. A number of radio wave sent from an antenna. (Multi-beam antenna has multiple beams.) Rules of communication. Procedure of data transmission, modulation scheme, error recovery and other rules are specified in a protocol. Digital bit stream not modulated. Information added to the beginning of a data block for control. A burst sent from the NMC or ABS to the user terminal which contains the sync-code, slot assignment information, operation status of network, satellite orbit information, and so on. Selection or setting up of path of communication. Link layer of Open System Interconnection (OSI) model specified by ISO. For uplink, time slot on which the user transmits an association request; and for downlink, time slot on which reference bursts are transmitted 25

29 Application Experiment Ground Station Guidelines The First Edition December 10, 2003 The Second Edition November 27, 2006 Secretariat Space Communications Research Office Information and Communications Policy Bureau Ministry of Internal Affairs and Communications Central Common Government Office, No. 2 Bldg., 11th floor Kasumigaseki, Chiyoda-ku, Tokyo , Japan winds@ml.soumu.go.jp 26