Литература / UMTS-Report

Outdoor to indoor and pedestrian: 2048 kbps

Vehicular: 1048 kbps

A1.3.4 What is the maximum range in meters between a user terminal and a base station (prior to hand-off, relay, etc.) under nominal traffic loading and link impairments as defined in Annex 2?

Refer to section 2.4.

A1.3.5 Describe the capability for the use of repeaters

The proposal supports the use of repeaters. Repeaters are units receiving signals on UMTS carriers and transmitting the same information content on the same frequency with increased power. This does the repeater for up and downlink. The repeater does not take any action on signaling etc., and needs therefore only a main power connection and the antennas. Repeaters can be used in rural areas for enhancing cells with low traffic density. Or repeaters can be used in urban areas to improve the indoor coverage on certain areas. The transmission via the repeater has to fulfill a certain linearity in case of band repetition due to multi carrier transmission. Usually there is a radio channel between MS and BTS. In the repeater this results in a chain of radio channel, repeater, and radio channel. The total delay time of the repeater shall be fix, it was to be checked case by case, that the enhanced cell range, together with the repeater delay does not exceed the max. guard period time of the RACH.

The use of repeaters for this proposal requires the same level of planning activities like for repeaters in second generation TDMA systems. Repeaters are seen as an appropriate measure to enhance cell ranges in low traffic areas.

A1.3.6 Antenna Systems: Fully describe the antenna systems that can be used and/or have to be used; characterize their impacts on systems performance, (terrestrial only) e.g.:

-Does the SRTT have the capability for the use of remote antennas: Describe whether and how remote antenna systems can be used to extend coverage to low traffic density areas.

-Does the SRTT have the capability for the use of distributed antennas: Describe whether and how distributed antenna designs are used, and in which UMTS test environments.

-Does the SRTT have the capability for the use of smart antennas (e.g. switched beam, adaptive, etc.): Describe how smart antennas can be used and what is their impact on system performance.

-Other antenna systems.

WB-TDMA/CDMA does not require the use of smart antennas. But the resulting signal-to-interference- plus-noise-ratio (SINR) can be improved significantly by incorporating various smart antenna concepts at the base station on the uplink as well as the downlink. These SINR gains may be exploited

∙to increase the capacity (mainly in urban areas),

e.g., by reducing the cluster size, i.e., the number of cells per cluster, or by using 16 QAM instead of the QPSK data modulation,

∙to increase the coverage (mainly in rural areas), e.g., by increasing the cell size (range extension),

∙to increase the quality,

∙to decrease the delay spread,

∙to reduce the transmission powers,

or a combination thereof. In Section 2.3 three different smart antenna concepts, namely

∙diversity antennas,

∙sector antennas,

∙and adaptive antenna arrays,

and show how these smart antenna concepts can be incorporated into the joint detection (JD) processes used in WB-TDMA/CDMA. With 8 antenna elements, improvements of the spectral efficiency by a factor of three to more than five have been achieved for WB-TDMA/CDMA, depending on the chosen channel model and the employed smart antenna concept.

As opposed to GSM, the gains in capacity and range achieved by using smart antennas can be realized for all traffic channels, since the control channels that have to be broadcasted in an omnidirectional fashion are transmitted on a separate GSM-like 200 kHz carrier. To decrease the required cluster size of this broadcast control channel, unnecessary information is removed and the coding is increased with respect to GSM.

For further details on smart antennas see section 2.3.

But macro diversity requires that the measure is used throughout a larger area to gain from. For a simple enlarging of a cell it is sufficient to remote one RF front end. This remotization requires only a lower bandwidth, because it is possible to remote more signal processing and sending only the net data via the land-line. The land-line media may by copper or fiber, depending on the bandwidth requirements and the availability. The interface between central and remote unit will be a proprietary one, to have the full flexibility to optimize in terms of applications and internal function splits.

The remotized unit can be operated on an own frequency, or does the frequency share with a transceiver in the central unit. This sharing can be done by allocating dedicated time slots to one transceiver and other times lots to the other receiver. This will cause intracell handovers between the time slots, when a MS moves from one service area to the other.

The other option is to transmit and receive simultaneously, but instead with macro diversity schemes, the central unit decides simply which one of the base band signals shall be used, e.g. on a frame by frame basis. This does not require any extra land-line bandwidth. The proposal shows excellent performance in handling long delay spreads. Therefore, the MS does treat the sum of both signals as a single signal with long excess delay. However, this is not critical due to the power distribution versus delay.

Does the RTT have the capability for the use of distributed antennas: Describe whether and how distributed antennas are used, and in which UMTS test environments.

The proposal supports the use of distributed antennas on the same degree as it is feasible to do it with second generation TDMA systems. This option is useful to improve the indoor coverage, or to ensure urban outdoor coverage, whilst operating with very low antenna hights. All receive and transmit signals are combined onto their feeder cables. Instead of connecting the feeder cables to a single antenna, a splitter is used to distribute onto different antennas. By using the RF layer as the transport mechanism on the cables, the insertion loss of coax feeder cable will limit the remotization ranges to only some hundred meters. The splitter devices have of course to fulfill some linearity requirements to avoid unwanted intermodulations

A1.3.7 Delay (for voice)

A1.3.7.1 What is the radio transmission processing delay due to the overall process of channel coding, bit interleaving, framing, etc., not including source coding? This is given as transmitter delay from the input of the channel coder to the antenna plus the receiver delay from the antenna to the output of the channel decoder. Provide this information for each service being provided. In addition, a detailed description of how this parameter was calculated is required for both the up-link and the down-link.

The delay for voice service A (every second time slot) and voice service B (every time slot) is: Downlink: 19.1 ms consisting of channel coding 0.5 ms (implementation dependent) + margin 0.6 ms + interleaving 18 ms

Uplink: 5 ms consisting of joint detection receiver 3 ms + channel decoding 1.0 ms + margin 1.0 ms. In the uplink case the delay due to interleaving is associated with the mobile station.

The numbers refer to the delay to be expected in the BTS, based on interleaving over 4 blocks and state-of-the-art hardware implementation. The increased processing delays for uplink are due to the higher complexity of the joint detector and the channel decoder. In downlink there is no joint detection considered and there is only channel encoding.

A1.3.7.2 What is the total estimated round trip delay in msec to include both the processing delay, propagation delay (terrestrial only) and vocoder delay? Give the estimated delay associated with each of the key attributes described in Figure 1 of Annex 3 that make up the total delay provided.

The round trip delay figures are as follows

The portable round trip delay for voice is 51.2 ms.

The numbers are based on a state-of-the-art hardware implementation and a speech codec with 20 ms frame length. Included are margins for data transport, buffering, busses, etc. Not included are delays on the interface between the BTS and the transcoder and delays for A/D conversion in the portable. The propagation delays are negligible (< 0.1 ms) compared to the other delays.

The following figure shows how delays are associated with the different entities. The delay for speech decoding is 1.5 ms and for speech encoding 25 ms (20 ms speech frame + 5ms processing).

delay for voice service in ms

A1.3.9 Description on the ability to sustain quality under certain extreme conditions.

A1.3.9.1 System overload (terrestrial only): Characterize system behavior and performance in such conditions for each test services in Annex 2, including potential impact on adjacent cells. Describe the effect on system performance in terms of blocking grade of service for the cases that the load on a particular cell is 125%, 150%, 175%, and 200% of full load. Also describe the effect of blocking on the immediate adjacent cells. Voice service is to be considered here. Full load means a traffic loading which results in 1% call blocking with the BER of 10-3 maintained.

The proposal is characterized by a very high hot spot capability. Under mobility conditions the hot spot capability is at least a threefold capacity compared to an embedded cell. Under pedestrian conditions i.e. malls, convention centers, stadiums etc. the hot spot capability is at least six-fold.

The actual hot spot capability is determined by system deployment and installed base station equipment. Dynamic channel allocation (DCA) may be used to adaptively exploit the very high inherent hot spot capability of WB-TDMA/CDMA. In addition call redirection may be used to carry the offered traffic in one cell also by the adjacent cells. This feature will effectively realize a cell shrinking mechanism for a heavily loaded cell and enable traffic to be carried by adjacent cells.

A1.3.9.2 Hardware failures: Characterize system behavior and performance in such conditions. Provide detailed explanation on any calculation.

BTS failures are indicated by alarm reporting to O&M functions. Independent hardware reconfigurations are performed if control channels are concerned.

BSC failures are indicated as in GSM to the O&M functions. All BSC units are operated in hot stand by technology.

A1.4.3 Synchronization requirements: Describe SRTT’s timing requirements , e.g.

-Is base station-to-base station or satellite LES-to-LES synchronization required? Provide precise information, the type of synchronization, i.e., synchronization of carrier frequency, bit clock, spreading code or frame, and their accuracy.

-Is base station-to-network synchronization required? (terrestrial only)

-State short-term frequency and timing accuracy of base station (or LES) transmit signal.

-State source of external system reference and the accuracy required, if used at base station (or LES)(for example: derived from wire-line network, or GPS receiver).

-State free run accuracy of mobile station frequency and timing reference clock.

-State base-to-base bit time alignment requirement over a 24 hour period, in microseconds.

-For private systems: can multiple unsynchronized systems coexist in the same environment?

-Base station to base station synchronization is not required. The system is designed for unsynchronous operation.

-If of advantage or required, synchronized operation is possible, either with system internal means (like the German C-450 network) or via GPS. Accuracy ≈ 1μs.

-BTS synchronization to the network is useful like in GSM (for stability refer to A.1.4.1)

-Source stability of external reference frequency = ± 2N10-8

-Free run accuracy of mobile station and derived timing reference clock = ± 2.5N10-6

-Base to base bit time alignment over 24 hour = 200 μs.

-Multiple unsynchronized systems can coexist in the same radio environment.

A1.4.8 Characterize any radio resource control capabilities that exist for the provision of roaming between a private (e.g., closed user group) and a public UMTS operating environment.

The specific requirements for private systems as well as residential applications are very efficiently fulfilled by the WB-TDMA/CDMA proposal. Private systems include the whole range of applications from large multicell wireless PBXs to small single cell cordless telephones connected to the analogue or the ISDN PSTNs.

The fundamental requirement is coexistence of independent systems without any need for coordination, planning or common control

Coexistence in the same environment means that uncoordinated systems located in the same geographical area have to share the same frequency band. Successful coexistence means that the individual systems can efficiently cope with cross-interference between the independent running systems.

The basic conditions to meet this target are:

∙A resource division structure that requires no co-ordination or synchronization of the different systems and limits the cross-interference generated by one system to only very few other systems.

∙A Dynamic Channel Allocation (DCA) procedure including fast seamless handover between different channels that guarantees fast resource allocation, efficient use of the available spectrum (no need to split into upand downlink parts) and a stable operation of the systems.

∙A simple and fast method to detect the less interfered available portion of capacity.

∙An early collision detection that allows the initiation of a handover well before the whole data stream becomes corrupted.

The WB-TDMA/CDMA proposal fulfills all the above requirements. By the proposed TD-structure in combination with the moderate bandwidth of 1.6 MHz a 20 MHz wide frequency band for example will be divided into 80 to 96 separated blocks (depending on the required guard bands to adjacent services). Every block is defined by its time interval and its carrier frequency. Every block has a limited capacity of about 125/250 kbps. Assuming a well-designed DCA and an increasing demand on traffic or data rate for UMTS applications, this capacity in most cases will be allocated to one small system. The only interference from other systems will be from systems using adjacent frequency bands or adjacent time slots.

The problem of sliding collisions due to unsynchronized systems can be solved by proper implementations allowing to detect increasing data corruption at the beginning or the end of every burst.

Escaping from an interferer by seamless handing over to less interfered channels, requires the detection of suitable resources and the set-up of a second link in parallel to the running connection. In WBTDMA/CDMA this can be done for low and medium data rates without the need for a second transmitter hardware.

A1.4.9 Describe the estimated fixed signaling overhead (e.g., broadcast control channel, power control messaging). Express this information as a percentage of the spectrum which is used for fixed signaling. Provide detailed explanation on your calculations.

This is mainly dependent on layer 2 and 3 algorithms. Further details will be elaborated between milestone M2 and M3.

A1.4.10 Characterize the linear and broadband transmitter requirements for base and mobile station. (terrestrial only)

Compared to current existing 2nd generation systems (e.g. GSM) different modulation schemes and the multi code option are used in this proposal. Furthermore, on an RF frequency more than one subscriber will be transmitted. This will lead to higher linearity requirements due to additional amplitude modulation. However, in case of the base station these requirements can be fulfilled with existing of the shelf equipment.

data rate: 64kbps (QPSK) or 128kbps (16QAM)

data rate: 128kbps (QPSK) or 256kbps (16QAM)

spread burst 2 :

RAM and ROM size requirements for implementation are quite relaxed since the matrices considered for channel estimation and joint detection are extremely sparse. Joint detection and channel estimation do not necessarily have to be implemented with a DSP. A optimized implementation might use dedicated hardware of certain parts of the algorithms.

A1.4.15 Characterize the frequency planning requirements:

-Frequency reuse pattern: given the required C/I and the proposed technologies, specify the frequency cell reuse pattern (e.g. 3-cell, 7-cell, etc.) and, for terrestrial systems, the sectorization schemes assumed;

-Characterize the frequency management between different cell layers;

-Does the SRTT use interleaved frequency allocation?

-Are there any frequency channels with particular planning requirements?

-Can the SRTT support self planning techniques?

-All other relevant requirements

Note: Interleaved frequency allocation is to allocate the 2nd adjacent channel instead of adjacent channel at neighboring cluster cell.

a.) Frequency re-use pattern and sectorization scheme:

As can be seen from the detailed results of the link level simulations the required C/I to operate the system is significantly lower than for GSM (even if one takes into account that there up to 8 times as much interferers per time slot as for GSM); e.g. for speech the required C/I was found to be about -5 dB for the uplink and -3.0 ... -2.0 dB for the downlink for all environments. Hence, a smaller cluster size as for GSM is expected. The exact figures for the cluster size obviously depend upon the required grade of service. However, simulation results show that an omni cell cluster 3 is appropriate to operate the system, at least under fractional loading conditions. By using a sectorized clover leaf network of cluster 1/3 the threefold capacity per site can be achieved at nearly the same grade of service.

b.) Frequency management between different layers:

For isolated hot spot micro cells and indoor pico cells it is expected to re-use frequencies from the macro layer. In this case the frequency planning tool has to take into account interference between different cell layers. For contiguous micro cell coverage within a hierarchical cell structure separate frequencies should be assigned to different layers.

By using channel segregation, a dynamic separation between frequencies of different layers may be achieved.

c.) Interleaved frequency allocation:

Due to interference averaging, low values for the required C/I and an adjacent channel suppression of 15 dBc, it is possible to use adjacent frequencies in adjacent cells, hence no interleaved frequency allocation is used. However, adjacent frequencies within one cell should be avoided.

d.) Are there any frequency channel with special planning requirements?

No.

e.) Can the SRTT support self planning techniques?

Based on link quality measurements, priority levels can be assigned to each RF carrier in each cell. By this method a self planning by channel segregation is possible which also may be used for separating the frequency resources between different cell layers. Additional measurements by the MS - as discussed for future GSM phases - can be foreseen from the beginning for FMA 1 with spreading to support these self planning techniques.

f.) All other relevant requirements?

None.

A1.4.16 Describe the capability of the proposed SRTT to facilitate the evolution of existing radio transmission technologies used in mobile telecommunication systems migrate toward this SRTT. Provide detail any impact and constraint on evolution.

One of the basic intentions, which resulted in the WB-TDMA/CDMA proposal, is to facilitate the evolution from GSM900/1800 towards UMTS due to

∙same timing

∙carrier spacing is multiple of 200kHz

∙same clock rate as in GSM terminals

∙therefore, easy support of dual mode terminals

∙easy support of handover between UMTS and GSM

∙no softhandover required

For further details see section 2.2.

A1.4.16.1 Does the SRTT support backwards compatibility into GSM/DCS in terms of easy dual mode terminal implementation, spectrum co-existence and handover between UMTS and GSM/DCS?

∙Dual mode terminal: 2 duplexers and 2 RF filters are needed. All the other HW units are used for both UMTS or GSM mode.

∙Spectrum co-existence: GSM900/1800 and WB-TDMA/CDMA links can be active in adjacent frequency channels without a deterioration of the bit error rate, of course with respect to a certain guard band.

∙Handover: Efficient handover between GSM900/1800 and WB-TDMA/CDMA and vice versa for real time services during a call is possible due to the same timing. For non real time bearer services which can be established in both systems the handover will be lossless.