ITU/BDT Arab Regional Workshop on “4G Wireless Systems” - Tunisia 2010 ITU/BDT Arab Regional Workshop on ITU/BDT Arab Regional Workshop on “4G Wireless Systems” LTE Technology Session 5 : LTE Technology Perofrmance Evaluation Evaluation Speakers M. Lazhar BELHOUCHET M Hakim EBDELLI M. Hakim EBDELLI Date 27 – 29 January 2010 www.cert.tn 1 LTE Technology Perofrmance Evaluation
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ITU/BDT Arab Regional Workshop on “4G Wireless Systems” - Tunisia 2010
ITU/BDT Arab Regional Workshop onITU/BDT Arab Regional Workshop on“4G Wireless Systems”
ITU/BDT Arab Regional Workshop on “4G Wireless Systems” - Tunisia 2010
Frequency Bands : Typical deployment areas
• Europe:– Band 7:The 2.6 GHz auctions have been running in a few countries during 2007 and
2008, and continue during 2009/2010.
– Band 8:is currently used mostly by GSM. The band is attractive from a coverage point of view due to the lower propagation losses. The band can be reused for LTE or for HSPA.
– Band 3: is also used by GSM, but in many cases Band 3 is not as heavily used by GSM as Band 8. That makes refarming for LTE simpler.
– Digital dividend
• USA: Bands 4, 12, 13, 14 and 17. Bands 2 and 5 can be used for LTE refarming.
• Japan : Bands 1, 9, 11 and 18.
• LTE deployments globally will use several different frequency bands from the start.
ITU/BDT Arab Regional Workshop on “4G Wireless Systems” - Tunisia 2010
Layer 1 Peak Bit Rates
sSubCarrierofNumberHzbits
msSubFramepersymbolsofNumbersMbratebitPeak *)(*
1]/[ =
• control and reference signal overheads:– PDCCH: takes one symbol out of 14 symbols. That is the minimum possible PDCCH
allocation The resulting control overhead is 7 1% ( = 1/14)allocation. The resulting control overhead is 7.1% ( = 1/14).
– Downlink Reference Signals (RS) depend on the antenna configuration :Single stream transmission uses 2 RS out of 14 in every 3rd sub‐carrier, 2 × 2 MIMO 4 symbols and 4 × 4 MIMO 6 symbols The overhead varies between 4 8% and 14 3%symbols and 4 × 4 MIMO 6 symbols. The overhead varies between 4.8% and 14.3%.
– Other downlink symbols Overhead: synchronization signal, PBCH, PCFICH, and one group of PHICH. The overhead depends on the BW ranging from below 1% at 20 MHz to approximately 9% at 1 4 MHzMHz to approximately 9% at 1.4 MHz.
– Uplink reference signals take 1 symbol out of 7 symbols resulting in an overhead of 14.3% = 1/7.
ITU/BDT Arab Regional Workshop on “4G Wireless Systems” - Tunisia 2010
Link Budgets
• The link budget calculations estimate the maximum allowed signal attenuation between the mobile and the base station gantenna. The maximum path loss allows the maximum cell range to be estimated with a suitable propagation model.
• The cell range gives the number of base station sites required to cover the target geographical area.
Parameters Unit Significance Parameters Unit SignificanceLu dB Path loss in Urban Areas f MHz Frequency of TransmissionhB m Height of base station Antenna CH dB Antenna height correction factorhM m Height of mobile station Antenna d km Distance between Base station and MS
ITU/BDT Arab Regional Workshop on “4G Wireless Systems” - Tunisia 2010
Link budgets Comparison GSM/HSPA/LTE• The LTE link budget in downlink has several similarities with HSPA and the
maximum path loss is similar.
h l k h d ff ll f• The uplink part has some differences: smaller interference margin in LTE, no macro diversity gain in LTE and no fast fading margin in LTE.
• The link budgets show that LTE can be deployed using existing GSM and HSPA sites assuming that the same frequency is used for LTE as for GSM and HSPA.
• LTE itself does not provide any major boost in the coverage. That is because the transmission power levels and the RF noise figures are also similar in GSM and HSPA technologies, and the link performance at low data rates is not much different in LTE than in HSPA.
• The link budget was calculated for 64 kbps uplink, which is likely not a high enough data rate for true broadband service. If we want to guarantee higher data rates in LTE, we may need low frequency deployment, additional sites, active antenna solutions or local area solutions.
ITU/BDT Arab Regional Workshop on “4G Wireless Systems” - Tunisia 2010
Difference between 900 MHz and 2600 MHz
Urban RuralRural fixedwireless
• 1 :According to Okumura–Hata.
• 2 :Shared 1.3 m antenna for / d d
Propagation loss (1) +14 dB +14 dB +14 dB
BTS antenna gain ‐3 dB (2) 0 dBc 0 dB (3)
900/2600 giving 15 and 18 dBigain at 900 vs 2600 MHz.
• 3 :2.5 m antenna giving 18 dBi gain at BTS antenna gain 3 dB (2) 0 dBc 0 dB (3)
BTS cable loss (4) +1 dB +3 dB +3 dB
900 MHz.
• 4 :Cable 1/2’. Urban 30 m and rural 100 m.
UE antenna gain ‐5 dB (5) ‐5 dB (5) 0 dB (6)• 5 :Based on 3GPP RAN4
contributions.
• 6 :External fixed antenna assumed. UE sensitivity (7) ‐1 dB ‐1 dB ‐1 dB
Total +6 dB +11 dB +16 dB
• 7 :UE sensitivity can be up to 3 dB worse at 900 MHz but thedifference in practice is less.
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difference in practice is less.
LTE Technology Perofrmance Evaluation
ITU/BDT Arab Regional Workshop on “4G Wireless Systems” - Tunisia 2010
Cell range Limitation
• The earth’s curvature limits the maximum cell range to approximately 40 km with an 80 m high base station antenna pp y gassuming that the terminal is at ground level.
• The maximum cell range can be calculated with Equation below
• To achieve 100 km cell range, the required antenna height is 580 m!!!
R = 8650 km hRdR +=+ 222 )((Effective earth radius for radio propagation is4/3 larger than real radius)
ITU/BDT Arab Regional Workshop on “4G Wireless Systems” - Tunisia 2010
Latency
• User plane latency is relevant for the performance of many applications. pp
• There are several applications that do not require a very high data rate, but they do require very low latency: voice, real time gaming, interactive applications.
ITU/BDT Arab Regional Workshop on “4G Wireless Systems” - Tunisia 2010
LTE Refarming to GSM Spectrum
• LTE could be deployed in the existing GSM spectrum like 900 MHz or 1800 MHzlike 900 MHz or 1800 MHz.
• The flexible LTE bandwidth makes refarming easier th ith WCDMA b LTE t t ith 1 4than with WCDMA because LTE can start with 1.4 MHz or 3.0 MHz bandwidths and then grow later h th GSM t ffi h d dwhen the GSM traffic has decreased.