Require Doc on Antenna Hopping

[parsarka]

Dear Experts,
Please share a NSN doc which describes in details the functionality of Antenna Hopping and its impacts on RX Quality ,SD drop,TCH Drops

[makeev]

Hi, Find attached an NSN document that explains all about antenna hopping.

[usama0795]

The Antenna Hopping feature helps to avoid network level interference and link level frequency selective fading. With the Antenna Hopping feature, the user can achieve in average 2 dB gain on the link level. With low antenna correlation, Antenna Hopping can gain 1.5 to 4 dB depending on the mobile speed (typical urban, 3 to 50 km/h, no FH) compared to a single antenna and it showed quite a improvement in TCH Drops and SD Drops......but with antenna hopping enabled it does not support DFCA and OSC features........and good thing is unlike DFCA and OSC u dont need to change any other parameter just change to 1 and see the improvement.


**Antenna Hopping is a further improvement for the performance of RF or BB hopping. In antenna hopping, also the BCCH frequency is fully hopping between 2 or more antennas.
Antenna Hopping enables the TRXs in an RF hopping BTS to transmit with all the TX antennas in the BTS. Antenna Hopping uses the existing baseband (BB) hopping functionality in the BTS.

[fariezqi53]

if I want to buy where, if I make own out approximately how much money





forgive the English language

[usama0795]

Very old feature in E******* and has got very good explanation from Alex:

1 Introduction (http://www.finetopix.com/#TOP)During a call connection, a burst can easily be lost when the mobile station happens to be located in a fading dip for that particular frequency, or if it is subjected to interference. The coding and interleaving scheme in GSM is constructed so that loss of a single burst has minimal influence on the speech quality. The probability that several bursts within a speech frame have poor signal quality is reduced if the bursts are transmitted on different paths. This can be done using antenna hopping. With antenna hopping, transmit diversity is introduced by altering transmit antenna between bursts. In Figure 1, S is the transmitted signal. Transmit diversity scheme in Figure 1 mimics frequency hopping in the sense that the fading changes rapidly between bursts due to transmission through different paths S1 and S2.

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Figure 1 Schematic picture of antenna hopping
From a subscriber point of view, antenna hopping gives an improved speech quality. From an operator point of view, antenna hopping is a very attractive scheme in particular for channels without frequency hopping. It has also advantages for traffic channels with frequency hopping over a relatively low number of frequencies (less than 8). What makes antenna hopping interesting as a transmit diversity scheme is the fact that it can be used without increasing the number of TRXs in a base station. Thus giving the operator the following benefits:

more robust radio environment
improved signaling performance
possibility to give subscribers a more uniform speech quality
[URL="http://www.finetopix.com/#TOP"]Capabilities (edw:/alex?ac=image&fn=223_1553-HSC10312Uen.A4-S.eps.pdf)

The main idea of antenna hopping is to level out the fading dips in received signal strength that occurs due to multipath propagation. With antenna hopping, a non-moving mobile will typically remain in a specific fading dip no longer than one TDMA frame. The low signal strength dips in multipath fading are thus leveled out, and the mobile will perceive a more constant radio environment. This is particularly suitable for non frequency hopping common channels such as BCCH. The transmit diversity is obtained through antenna hopping, by switching transmit antenna between bursts. The benefit is fully utilized through coding and interleaving. Antenna hopping on BCCH carrier mimics frequency hopping by providing diversity between bursts with regard to the fast fading. It can serve as an alternative to frequency hopping on traffic channels without frequency hopping. Also for traffic channels that use frequency hopping over a limited number of frequencies, this feature can be used as a complement in order to increase the diversity.
Figure 2 is illustrating the received signal strength. The dashed line is the received signal strength with multipath fading at antenna "1" , the thin line is the received signal strength with multipath fading at antenna "2" and the bold line is illustrating the diversity gain achieved by using antenna hopping.

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A distinction between antenna hopping and frequency hopping in an interfered radio environment, is that with frequency hopping, a mobile is interfered by different base stations in different bursts, i.e. "interference diversity". With antenna hopping and no frequency hopping, the same interference is present in all bursts, this means that only the fast fading changes between the bursts.
The advantage of this feature is more evident with slow/non-moving mobiles than the fast moving mobiles. The fast moving mobiles can obtain similar improvements by their speed alone. Antenna hopping improves the sensitivity of the receiver, in terms of reported FER values for low speed/stationary users under condition of low signal strength. This improvement can indirectly be interpreted into improved network performance. Simulations have shown that substantial gains can be expected for coding schemes with low code rates, e.g. EFR, AMR, GPRS CS1 and CS2 as well as EGPRS MCS-1, MCS-2, MCS-5 and MCS-6. Codecs with high code rate due to less error correction rate, e.g. EGPRS MCS-4 and MCS-9, on the other hand, may suffer from antenna hopping depending on hopping sequence. Other codecs, MCS-3, MCS-7 and MCS-8 are not affected by antenna hopping.
For the special case of half rate channels, where the channel is sent every second burst, altering antenna on every burst would result in no transmit diversity in a two antenna configuration. By transmission of the first two bursts via the first antenna and the next two bursts via the second antenna and so on, the antenna hopping gain will be achieved for half rate channels as well. However a poor antenna system can hide the performance gain and have impact on feature capabilities. See chapter 4.6.

3 Technical Description (http://www.finetopix.com/#TOP)3.1 General (http://www.finetopix.com/#TOP)Antenna hopping is activated per transceiver group (TG). No possibility exist to select that antenna hopping shall be activated for only a part of the TG, e.g. only for one antenna system (sector). When activating the feature, it is possible to select if the channels on the BCCH frequency/frequencies shall be excluded from antenna hopping .
3.2 Algorithm (http://www.finetopix.com/#TOP)3.2.1 General (http://www.finetopix.com/#TOP)When antenna hopping is activated the RBS groups the enabled transmitters into antenna hopping sets (AHS). The transmitters in an AHS are selected such that at least two antennas in an antenna system are addressed. All selected transmitters must have identical radio capabilities (including nominal power and modulation capabilities) and fulfill the transmitter dedication information as stated in section 3.2.2.
Antenna hopping is started on each AHS when the AHSs has been created. The hopping is performed such that the following pattern is achieved:

Target antenna = (FN + (FN DIV 2)) MOD 2, if the number of antennas is two. Note: This pattern is selected to achieve transmit diversity gain even for half rate channels, where the channel is sent every second burst

Target antenna = FN MOD Nant, if the number of antennas is three or more.
Where FN = Frame Number and Nant = number of antennas.

MOD is defined as:
If m, n and p are integers, then m and n are modulo p , m=n mod(p) , if m-n is a multiple of p, i.e. m/p and n/p have equal remainders.

If antenna hopping is activated and there is a fault on a TRX or if the TRX is taken out of service, then antenna hopping automatically gets reconfigured and continues on the remaining TRXs.
3.2.2 Dedicating Transmitters to Cell and Channel Groups (http://www.finetopix.com/#TOP)If external equipment is used in the transmit chain (e.g. external power boosters), the capabilities of the transmitters are not enough to ensure that the radio capabilities of the transmit chains are identical. Therefore additional input is needed to the transmitter selection algorithm when the AHSs are built. To handle this, antenna hopping reuses the existing possibility to dedicate a transmitter to cell or (cell and) channel group. How this information is used when building the AHS is described in Table 1 (http://www.finetopix.com/#Table1).

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[usama0795]

3.4 GPRS/EGPRS Impact (http://www.finetopix.com/#TOP)

In antenna hopping, all GPRS/EGPRS channels are treated the same way as traffic channels. The advantage of this feature is more evident with low codec rates. Codecs with high code rate, due to less error correction rate, may suffer from antenna hopping depending on hopping sequence, see chapter 2, on GPRS-EGPRSimpacts (http://www.finetopix.com/#GPRS-EGPRSimpacts)
3.5 Related Counters (http://www.finetopix.com/#TOP)

There is no counter that is directly related to antenna hopping. For further information, please refer to Reference [3] (http://www.finetopix.com/#udRadioNetworkStatistics).
4 Engineering Guidelines (http://www.finetopix.com/#TOP)

4.1 General (http://www.finetopix.com/#TOP)

Antenna hopping is an optional feature and is beneficial on non-frequency hopping channels and channels with frequency hopping over a limited number of frequencies. The transmit diversity obtained through antenna hopping improves the receiving quality for slow moving mobile stations, thus balances the quality between slow and fast moving mobile stations. Slow and fast moving users can thereby be treated in the same way when designing the radio network. Transmit diversity can be seen as both considerable gain in FER as well as C/N at a given quality. It is recommended to run antenna hopping on cross polarized antennas.
4.2 Antenna Hopping Gain (http://www.finetopix.com/#TOP)

The gain from antenna hopping depends on factors such as propagation environment, signal strength, number of antennas to hop on, number of hopping frequencies and interference characteristics. The antenna hopping gain increases with the number of antennas to hop on. However this is not a linear equation. For example, increasing the number of antennas from two to three does not give as much improvement as increasing it from one to two. Two antennas per cell result in a substantial gain and are usually sufficient. Both simulation activities and field trials indicate that an average quality gain of 2% unit FER is achievable after activation of antenna hopping on BCCH carrier. Performance improvement by lower FER values, indicates a coverage improvement, see Table 2 (http://www.finetopix.com/#Table2). When antenna hopping is used in combination with frequency hopping the gain from antenna hopping decreases when the number of frequencies available for frequency hopping increases. The following table can be used as an approximation for the expected gain from antenna hopping in a typical urban (TU) environment. The expected gain in other environments may be smaller.

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4.3 Configuration Presumptions and Possibilities (http://www.finetopix.com/#TOP)

An antenna hopping enabled configuration needs two transmit antennas or a dual-polarized antenna in at least one antenna system. If some of the antenna systems have more than one transmit chain and others do not, only those with more than one transmit chain will be hopping.
Adding more than two transmit chains to an antenna system is possible (and in some configurations necessary) and antenna hopping will make use of all available transmit chains for hopping.
4.4 Applicability (http://www.finetopix.com/#TOP)

Antenna hopping can be applied on:

any CDU-G configuration of RBS 2106/2107/2206/2207,
any CDU-J configuration of RBS 2107/2207,
RBS 2108, 2109, 2111, 2116, and 2216
RBS 2308/2309 except RBS 2308/2309 with RBS 2302 as extension cabinet(s)
Note that some additional restrictions on supported RBS configurations exist. In order to get antenna hopping feature to operate, it is required that the same TRX capability exists on both TX-antennas in the cell. One example is mixed EGPRS/non-EGPRS configurations where different TRX-capabilities are used in same TG. Antenna hopping is only supported within a TG, meaning that it is not supported between cabinets using TG-synchronization.

4.5 Antenna System (http://www.finetopix.com/#TOP)

It is of importance that all antennas in a cell are pointing in the same direction. The reason for this is that the received signal strength from the cell is averaged. If the antennas are not pointing in the same direction, the measured average signal strength will decrease. This may cause change of cell borders when activating antenna hopping with reduced traffic capability as a consequence. Therefore, the vertical and horizontal alignments need to be checked carefully before deploying antenna hopping.
Figure 3 shows two antenna systems in one cell that are not covering the same area.

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If the downlink signal strength decreases or increases when activating antenna hopping, then there is a reason to evaluate the antenna installations. To avoid alignment problems between antennas, it is also recommended to use cross polarized antenna when the feature is activated. Due to the design of this antenna, the risk for misalignment will be minimized. A cross polarized antenna and an single antenna are shown in Figure 4 (http://www.finetopix.com/#Figure4).

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4.6 Degraded Antenna System (http://www.finetopix.com/#TOP)

Antenna systems with non-similar propagation performance and characteristics are called degraded antenna systems. Experiences from networks show that a degraded antenna system is a possible problem. Degradation can appear if the feeder connections are not properly done and some connectors may have additional attenuation. Antenna hopping could decrease the performance in a cell with a degraded antenna system.
4.7 Considerations Related to Combinations with other Features (http://www.finetopix.com/#TOP)

4.7.1 Antenna Hopping and Frequency Hopping in Combination (http://www.finetopix.com/#TOP)

It is beneficial to use antenna hopping on BCCH carrier and frequency hopping on TCH in combination, (see Reference [2] (http://www.finetopix.com/#udFreqHopping)). However, the gain from antenna hopping decreases as the number of frequencies available for frequency hopping increases. The gain from antenna hopping will be diminutive if there exist frequency hopping over more than eight frequencies.
It is possible to use antenna hopping in combination with both baseband hopping and synthesizer hopping. When antenna hopping is used in combination with baseband hopping, it is important to avoid cyclic frequency hopping to ensure that the gain is achieved from antenna hopping on BCCH. Setting HSN not equal to zero when frequency hopping is configured ensures that cyclic hopping is avoided and random hopping is used.
4.7.2 Antenna Hopping and TCC in Combination (http://www.finetopix.com/#TOP)

Antenna hopping is possible to use in combination with TCC (see Reference [1] (http://www.finetopix.com/#udBoostDownlinkOutputPower)). To achieve antenna hopping it is however important to fulfill that the capabilities (TCC configuration, modulation and min/max output capabilities) of the two transmit paths are identical. E.g. to make it possible to perform antenna hopping on the channels on a dTRU configured for TCC there has to be another dTRU with identical capabilities configured for TCC connected to another antenna in the same antenna system.
4.8 Impact of Antenna Hopping on Cell Planning (http://www.finetopix.com/#TOP)

4.8.1 General (http://www.finetopix.com/#TOP)

When planning a network, not only the sensitivity level of an MS should be considered but also various margins have to be added in order to obtain the desired coverage. Cell planning in a network is done with respect to these additional margins for signal strength levels. This level can be set to a lower value in a network using antenna hopping compared to a network without antenna hopping.
4.8.2 Cell Planning margins with Antenna Hopping on BCCH carrier (http://www.finetopix.com/#TOP)

There are several parameters that build up the required SS margin. One of them is called RFmargin (Rayleigh fading margin). According to RF Guidelines GSM 800, GSM 900, GSM 1800 and GSM 1900 (see Reference [4] (http://www.finetopix.com/#udRFguidelinedGSM800), Reference [5] (http://www.finetopix.com/#udRFguidelinedGSM900), Reference [6] (http://www.finetopix.com/#udRFguidelinedGSM1800) and Reference [7] (http://www.finetopix.com/#udRFguidelinedGSM1900)), Rayleigh fading dips on the BCCH can be leveled out by using antenna hopping on BCCH carrier, thereby improving sensitivity performance. This increases the variation rate of SNR which creates channel conditions that are more comparable to faster moving MSs
4.9 Impact of Antenna Hopping on Frequency Planning (http://www.finetopix.com/#TOP)

4.9.1 BCCH Carrier (http://www.finetopix.com/#TOP)

Antenna hopping on BCCH carrier is not designed to have considerable impacts on the frequency planning in general. Antenna hopping can give improved performance on the control channels BCCH/CCCH. This improvement can not necessarily be used for tighter BCCH frequency reuse since there may be other limiting factors e.g. Locating performance (i.e. base station selection). However, with the assumption that it is the speech quality on channels on the BCCH carrier that is the limiting factor, antenna hopping can facilitate tighter frequency reuse if the cells are designed for slow moving users.
4.9.2 TCH Carrier (http://www.finetopix.com/#TOP)

Antenna hopping can also be used for TCH channels and will give improved performance by increasing the diversity gain. It results in a more robust and reliable network utilizing the diversity gain achieved from antenna hopping. The improved performance can possibly be used for frequency planning. Antenna hopping may facilitate a tighter frequency reuse. However, the major aspect is the quality at fading dips for stationary users.