Minutes of Expert Online-Aug,2001
Mr.Karl Kammerlander,Senior Consultant and Advicer for the design of advanced 3rd Generation Mobile Radio Systems of Siemens Mobile Radio Division

Mr. Karl Kammerlander
Karl Kammerlander was born in Munich, Germany in 1930. He received his technical degree in the field of RF- and communication techniques in 1956 at Darmstadt, Germany. In 1965 he joined SIEMENS Communication Laboratories. He was involved in UHF wave propagation research, system planning, development and field tests of military digital mobile radio systems and designed the German public land mobile network PLMN C-450. He has been further active in national, European and international standardization as well as technical IPR Analysis in the field of digital mobile radio communications. Since 1994 he is active in the Siemens Mobile Radio Division as a Senior Consultant and Advicer for the design of advanced 3rd Generation Mobile Radio Systems.

Q: Hi, Mr. Kammerlander, many people now are interested at TD-SCDMA, can you give us a introduction about its developing in China?
A: Hi, everybody, I enjoy to answer your questions. Time scale in short: Cooperation between China and Siemens to develop TD-SCDMA was started in June 1998. First call demonstration took place on 11.April 2001. Field test trial system will start in Oktober 2001. Commercial products will be available in end of 2002.

Q: Mr. Kammerlander, Siemens declared that they will concentrate on TD-SCDMA, does this mean they decide to give up TD-CDMA?

Q: Why does Siemens give up High chip Rate TDD (= TD-CDMA)?
A: High chip rate TDD has been given up in the run of harmonizing the development and market strategy. Low chip rate TDD shows same effective data throughput and higher flexibility to adapt to small spectrum assignments. Effective data rate per user from 8 kbps speech up to 2Mbps packet service (Internet) is transmitted.

Q: As far as I understand, even the best technology has some weakness. Is there any weakness of TD-SCDMA?
A: TD-SCDMA has quite a lot of advantages, however, due to TDD operation the TRX efficiency is dropped by a factor of 2. The harmonized development of the more flexible 1.6 MHz carrier technique allows to re-increase TRX-efficiency by multi carrier techniques.

Q: I am newcomer, could you tell me where or how to find more resources about TD-SCDMA?
A: More resources you can find via CWTS webside: www@cwts.org.cn

Q: What does European operators think of TD-SCDMA solution?
A: We think European operators will appreciate the outstanding features, spectral efficiency and flexibility of TD-SCDMA.

Q: Mr. Kammerlander, what does the China operators think of TSM system? I heared they is not interested in TSM, isn't it?
A: TSM is the first step to show the excellent Mobile Radio Network performance of TD-SCDMA and allows to have a quick start up. With TSM all issues of radio performance of TD-SCDMA can be demonstrated. Further development steps will follow.

Q: I still have a lot of questions. Could you please leave a email addr. in some way? Thanks!
A: preliminary please mail to: Beate.Pils@icn.siemens.de

Q: Could you please let me know that if this standard is a public standard? If yes, where and how can I get it in details?
A: Yes, TD-SCDMA is a worldwide public standard approved by ITU and 3GPP. You can get details via CWTS website.

Q: Is there any group in charge of the modification of the standard? Are CATT and Siemens only?
A: CATT/Datang and Siemens are supported by the the Chinese standardization body CWTS, Chinese Operators as well as by members of the TD-SCDMA Forum as there are: Alcatel, Nortel, Motorola, Huawei, Racal and others. Since now TD-SCDMA has become a harmonized worldwide standard it is to expect that an increasing number of manufacturers and operators may join.

Q: WCDMA has 256 codes, but actually only 80 are used. How many percent of 16 codes of TD-SCDMA could be actually used?
A:TD-SCDMA can basically use all 16 codes, because it applies Joint Detection to eliminate Multiple Access Interference (MAI), those intracell interference caused by CDMA operation. Further, Smart Antennas are applied to minimize inter-cell interference. However, since 16 codes represent the blocking point per timeslot, 12 to 14 codes per timeslot will be used for a QoS of 1 to 2 %. In this way TD-SCDMA can use 75 to 85 % of the 16 codes.

Q: If a subscriber changes his bitrate during a call, e.g. from 12.2k to 384k, how fast the system could ensure?
A: A: The system is fully controlled by DSP software hence, it can change the bitrate from lowest to highest value from one block to another within each frame.

Q: Mr. Kammerlander, the frequency is precious, is the requirement of 1.6MHz band practical in the deployment engineering?
A: There is no problem at all in frequency precision of 1.6 MHz carriers since a low precision of 1ppm leads to about 2 kHz deviation. By the way, take reference to GSM with a bandwidth of 200 kHz.

Q: If the handover between TD-SCDMA and GSM or FDD will be supported?
A: The handover between TD-SCDMA and GSM or FDD will be supported

Q: What's process about JD technique?
A: JD technique supports higher channel load factors by minimizing multiple access interference as caused by CDMA multipoint to point access. It further increase dynamic range of multi signal detection to enable TD-SCDMA/TDD transmission.

Q: Any 3GPP paper pertains the TDSCDMA performance evaluation in Macro vehicular (120km/h)?
A: The speed performance of 120 km/h is correct only for the first step of trial system development further development support an increase up to 500 km/h.

Q: According current art status, will TD-SCDMA UE support JD or Rake?
A: TD-SCDMA UE will exclusively support JD.

Q: Is there any modification on A-interface in the first step of deployment?
A: The A interface will be similar to GSM respective GPRS and EDGE.

Q: Mr. Kammerlander, according to your opinion, what's the max. data speed for TD-SCDMA, maybe with some advanced technologies
A: The presently planned maximum date speed for 8-PSK modulation scheme is 2 Mbps. However, in some further steps for indoor and pico cell applications this value can be multiplied by some factors applying higher order modulation schemes.

Q: What's the Spreading Factor and number of TSs occupied by 8PSK 2Mbps transmission?
A: 8PSK 2 MHz transmission is exclusively applied for serial packed switched signals and Internet services.The maximum data speed is achieved by TDMA techniques without spreading, since spreading techniques representing CDMA can only effectively be applied for parallel transmission of relatively low bitrate signal sources.

Q: What's the progress of DCA? In what level?
A: DCA-techniques can effectively be applied only in TDMA based burst transmission techniques. DCA techniques are applied in 3 complimentary ways in TD-SCDMA:
1. Time domain DCA to select the minimum interfered timeslot,
2. Frequency domain DCA to select the minimum interfered carrier,
3. Space domain to select the minimum interfered direction by Smart Antennas.
With this provisions TD-SCDMA is automatically minimizing system self interference.

Q: What is the TD-SCDMA capacity?
A: It is easy to calculate: 7 TS per frame, 1 TS for Random Access = 2 x 3 TS per TDD direction with 16 codes each = total maximum number of 48 duplex 8 kbps users per radio carrier of 1.6 MHz. For a QoS of 1 % " 36 user per carrier, for a QoS of 2 %. " 40 duplex user per carrier.

Q:Such a capacity calculation is only applied for one single cell. However, such a capacity calculation is not proper for the multi-cells.
A: Okay,. in TD-SCDMA - based on operation of multi user "Joint Detection" and "Smart Antennas" - full 1.6 MHz-carrier capacity per cell is achieved in cellular reuse scenarios if a cellular reuse factor of
c = 3 is applied. Please take into regard that the minimum required spectrum is 5 MHz. Hence, for each cell a full 1.6 MHz TD-SCDMA-carrier is available. Also the former capacity calculation was made for one 1.6 MHz carrier respective one cell.

Q: Is TD-SCDMA designed for pico-cell or macro-cell, or other cells?
A: TD-CDMA was designed for indoor and hot spot service areas. However, TD-SCDMA, the
LCR-TDD is designed to operate in all radio environments from indoor up to macro cells without restrictions.

Q: Mr. Kammerlander, as TD-SCDMA coverage is 10 km only, it cannot be used as macro-cell?
A: This argument has often been used and is based on the simplified physical consideration that with a permitted MS-peak power of 1 Watt (+30 dBm) - according to the TD-SCDMA burst mode transmission of 1/7 (7 burst per frame) - the average power is reduced to 140 mW related to a drop of 8,5 dB reducing the radio range by a factor of "2 and corresponding area coverage by a factor of " 4.
However, in this consideration is suppressed that TD-SCDMA has a bandwidth gain of 5 dB by a reduced bandwidth of 1.6 MHz compared to 5 MHz for FDD as well as an additional gain by Smart Antennas of 8 dB. Consequently, 1.6 MHz TD-SCDMA shows 4.5 dB more coverage as 5 MHz FDD, respective a 1.35 higher radio range resulting in a 1.8 higher area coverage. Hence, TD-SCDMA constitutes the most powerful system of 3G to cover macro cells.

Q: How many subscribers are supported by 1 beam of SA?
A: Each subscriber is supported by an individually beam since direction and movement may be different.

Q: Will 8-element circular array smart antenna support sectorized cell? How?
A: Yes, 8-element smart antennas will support secorized cell by special SA development.

Q: Will the SA pattern change for each TS?
A: Yes, the pattern will change for each timeslot since there are differently distributed and moving users within each TS.

Q:How many beams formed in one TS for 8-E array in omnidirectional cell and sectorized cell?

Q: Will the SA 16 simultaneous beam patterns (for voice) change for each TS?
A: Yes. Smart antennas in TD-SCDMA will operate independent beam patterns in parallel per TS as well as other beam patterns in other TS: 16 independent beams per timeslot = 48 beams for duplex traffic per frame. For a 3 multi carrier TRX a maximum number of 144 beams per frame are operated.

Q: How does SA work if there is no line of sight path?
A: Smart antennas have the general ability to answer over the strongest path in case of strong influence of multipath propagation.

Q: Will the same 8-element circular SA be used in omni- and sector- cell? Any difference of beam numbers?
A: R&D work of this Item and optimization is still going on. For sectorized cells the smart antenna may have other configuration.

Q: Will circular array SA be used in sectorized cell? Thanks!

Q: Then each sector will be equipped with one 8-element array SA?
A: Circular array SA can basically be used in sectorized cells. However, special developments are going on.

Q: If use 12.2kbps (AMR voice), it seems there is only eight SF8 available per TS? What's the difference between 12.2k voice and 8k voice?
A: The spreading factor SF remains constant 16 for 12.2 kbps but 2 resource units (codes) are used. AMR voice allows for flexible operation in bitrate without remarkable changes in speech quality. With 8 kbps voice, one resource unit per user is assigned.

Q: Which will be dominant? 12.2k AMR voice (8 users per TS) or 8k voice (16 per TS)
A: With trial system, 12.2 k AMR voice will be used due to the restrictions of TRAU within the GSM network. For the final versions, 8 kbps AMR voice will be used.

Q: Will FDD use the 8k AMR? Is it better to use the uniform coding format for multi-mode UE?
A: The AMR coder means Adaptive Multi Rate coder. Since it is flexible in bitrate, a fixed coding rate is not required. The introduction of AMR was initiated by FDD (Qualcomm IS-95) to adapt to different traffic relations like DTX operation by changing SF. This procedure is a part of FDD operation.

Q: 48 8k voice user/carrier/TS is the theoretical limit? We care more of the actual capacity. A serious simulation or link budget supported by trial is more convincing. Is that right?
A: You are right. 48 8k duplex voice user per carrier is the theoretical limit. For a QoS of 1 to 2 % the number of duplex user per carrier is 36 to 40.

Q: Is QoS of 1% the blocking rate?
A: Regarding QoS of 1% leads to a minimum of 36 speech channels per carrier. The blocking rate depends on the QoS an operator is offering.

Q: Except for blocking rate, any other QoS of voice? Packet dropping rate?
A: Voice quality according to AMR, packet dropping rate lower than 0.1% based on ARQ techniques.

Q: So Qos of 1% mean the AMR basic requirement cannot be met.
A: QoS of 1% means that due to erlang b losses 1% of calls is without success. This has nothing to do with the bit error rate for AMR operation which depends on C/I relations of radio transmission and message coding. Maybe the Question is not clear enough.

Q: 5MHz guard band is needed for LCR-TDD and FDD macro cell co-existence, is it right?
A: A guardband of 5 MHz is exclusively required for a channel spacing of 5 MHz i.e. HCR-TDD. If FDD operation is concerned the guardband is required even twice, 5 MHz for uplink and 5 MHz for downlink = 10 MHz in total.
However, LCR-TDD (= TD-SCDMA) operate with 1.6 MHz channel spacing.
In TDD operation the guardband is alternatively used for both links. Therefore , TD-SCDMA requires only one time 1.6 MHz guardband to ensure general co-existence with other services as well as coexistence of MR services at the same tower and dislocation of operators.
The layout of TD-SCDMA guarantees Electro Magnetic Compatibility (EMC) to all radio services and it does not transmit radio power out of the assigned spectrum. This ability is based on use of guard band and protection filters. It is not sure that all competing systems do show equivalent performance.

Q: However, guard band has only 16 chips for the traffic burst.
A: There are two different things: The guard time within each burst of TD-SCDMA amount to 16 chip in time domain. This has nothing to do with guardband for frequency domain carrier separation to other services. The guard band used in TD-SCDMA is 1.6 MHz corresponding to one carrier bandwidth.

Q: Mr. Kammerlander, how is the interference issue between two TD-SCDMA operators using adjacent frequency band resolved?

Q: If adjacent cells have different switching point, the interference btw. them is huge, will this offset the TDD flexibility
A: By using one guard band of 1.6 MHz and filters, there is no interference between 2 TD-SCDMA operators using adjacent spectrum and/or different switching point. Moreover, with a cellular reuse factor of c=3 there is even a frequency isolation between carriers of the same BS.

Q: Mr. Kammerlander, 5 MHz is needed for LCR-TDD and FDD macro cell co-existence by CATT calculation, is it right?
Yes, basically 5 MHz guardband is required only by FDD: However, if FDD and TDD is operating in adjacent parts of spectrum it is easily possible for the lower 1.6 MHz transmission of TD-SCDMA to cut down spurious transmissions within the same guardband. In general, a lower bandwidth service can utilize a higher service guardband. Consequently, the CATT calculation is correct. But this does not mean, that TD-SCDMA requires a guardband of 5 MHz in general.

Q: It is said that the TD-SCDMA experimental system has been demonstrated without Smart Antenna. Is it right?
A: Due to the collocation of MS and BTS in Lab, no additional PA is required. In this case also Smart Antennas are not required. However, when we go on air by our Trial-and Demo-System Smart antennas are integrated.

Q: What is the status of TD-SCDMA system R&D? What is the plan of the R&D? When the filed trial is conducted.

Q: When will the whole system be tested? Including speech & data service
A: The field trials will be started in October this year and continued step by step.

Q: Will the asymmetric transmission be supported in Siemens first commercial version next year?
A: Yes, asymmetric transmission will be supported.

Q: How about the test equipment, protocol testers, for instance?
A: Equipment testers are under development.

Q: What is the consideration of TD-SCDMA handset?

Q: Mr. Kammerlander, when TD-SCDMA handset is available? It is TD-SCDMA and GSM dual mode or TD-SCDMA, GSM and UMTS tri mode?
A: The development of handsets is in progress and in plan. First issue will be TD-SCDMA/GSM.

Thank you all and good-bye and Servus!

Karl Kammerlander

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