Frequency Coordination Between UMTS and GSM Systems at 900 MHz

Transcription

1 Frequency Crdinatin Between UMT and GM ystems at 9 MHz Vieri Vanghi, Mustafa aglam, and Jiang Jindi QUALCOMM Incrrated 5775 Mrehuse Drive, an Dieg, CA [email protected], [email protected] Huawei Technlgies C., LTD Huawei Industrial Base, Bantian Lnggang henzhen, P.R.China [email protected] Abstract UTRA-FDD requirements fr eratin in the 9 MHz band have been recently standardized in 3GPP aving the way fr refarming f GM sectrum t UMT. UMT9 netwrks will have t c-exist with GM9 netwrks fr sme time. 3GPP [1] has studied c-existence issues and has cncluded that GM9 and UMT9 can c-exist in bth crdinated and un-crdinated delyments in which the UMT9 carrier is allcated 5 MHz in additin t a guard-band equal t 1 GM channel (2 KHz) n each side. Hwever, in sme delyments the eratr may nt have sufficient available GM sectrum t allw the GM traffic t be ffladed frm the sectrum allcated t UMT9 t the remaining GM sectrum. Hence f interest is t assess system erfrmance under much mre stringent sectrum clearing assumtins. Here we characterize transmitter and receiver erfrmance based n lab tests cnducted n cmmercial equiment, bth UMT9 and GM9 terminals and base statins. Frm such measurements we assess the imact f mutual interference, GM M with UMT NdeB and UMT UE with GM BT, n receiver erfrmance as a functin f frequency ffset and culing lss between interfering transmitter and ffended receiver. We shw that the limiting factr is the interference caused by the GM M t the UMT Nde B, and that as little as 4.2 MHz f GM sectrum can be cleared and allcated t ne UMT carrier with satisfactry system erfrmance. 1 Intrductin UMT9 cmbines the benefits f WCDMA with better ragatin advantage at lwer carrier frequency. UMT9 ffers CAPEX gains (less number f NdeBs) in rural mrhlgies and better in building enetratin in urban mrhlgies cmared t UMT21. UMT9 and GM9 are exected t c-exist in Band VIII. The delyments can be in crdinated r uncrdinated mde. Crdinated eratin requires ne-t-ne verlay f UMT9 NdeBs with GM9 BTs. The lcatins f tw technlgies sites are nn-cllcated in uncrdinated eratin. [1] and [6] recmmend cnservative carrier t carrier searatin: 2.6 MHz fr crdinated eratin, 2.8 MHz fr uncrdinated eratin. This aer studies the required guard band between UMT9 and GM9 in crdinated and uncrdinated eratin using lab test measurements with cmmercial GM BT, UMT NdeB and dual mde handset. ectin 2 describes the transmitter and receiver characteristics and exlains the calculatin f adjacent channel interference rejectin (ACIR) using the measurements in the lab. ectin 3 resents hw the sensitivity f victim receiver is degraded based in the interferer strength and culing lss between the interferer and the victim. Mutual interference between GM M and UMT Nde B and mutual interference between UMT UE and GM BT are studied. Cnclusins are summarized in ectin 4. 2 Transmitter and Receiver Characteristics Mbile statin and base statin receivers can tlerate nly a certain level f adjacent channel interference withut suffering significant erfrmance degradatin. The rximity in frequency and sace with which UMT and GM channels can be lcated deend mainly n the netwrk design, and n the transmitter/receiver design. In articular, f interest are the ut-f-band emissins (OOBE) f the transmitter and the adjacent channel selectivity f the receiver. The transmit sectrum is affected by the baseband FIR filters, u cnversin t the desired carrier frequency and amlificatin. The amlifier nn-linearity causes intermdulatin effects, resulting in the transmit signal energy t sill int the adjacent channels. At the receiver, filtering is used t selectively suress ut-f-band interference. Tyically, AW filters are used at the first stage f filtering because they intrduce negligible amunt f distrtin. Fllwing stages f filtering with gd clse-in rerties further suress residual interference befre it can make its way int the AGC and then int the ADC f the receiver. Transmit and receive filters n the ulink (mbile statin interfering with base statin) and dwnlink (base statin interfering with mbile statin) determine the system adjacent channel interference rejectin (ACIR), defined in [3] as the rati f the ttal wer transmitted frm a surce (base r mbile statin) t the ttal interference wer affecting a victim receiver, resulting frm bth transmitter and receiver imerfectins. In [1], the ACIR is cmuted as ACIR = ACLR AC (1). where ACLR stands fr adjacent channel leakage rati [4], and AC fr adjacent channel selectivity [5]. The ACLR is the rati f wer in the adjacent channel t the wer in

2 the assigned channel. The AC is the rati f the receive filter attenuatin n the assigned channel frequency t the receive filter attenuatin n the adjacent channels. Nw ntice that Eq.(1) reresents nly a crude arximatin, as ACLR and AC give nly artial infrmatin n transmitter OOBE and receiver frequency resnse. Hereafter we then seek an accurate methd t estimate system ACIR based n lab measurements cnducted n cmmercial UMT9 and GM9 base statins and terminals. 2.1 ACIR Estimatin The ACIR can als be seen as the attenuatin L that the adjacent channel interference at frequency ffset f underges while making its way thrugh the receiver filter chain. L( f) can then be estimated by measuring the sensitivity lss caused by an adjacent channel interfering signal f knw wer level. Cnsider a receiver with nise figure F. The sensitivity f such receiver can be measured as the required signal wer received at the antenna cnnectr that results in a certain erfrmance, say a bit errr rate (BER) equal t.1%. We can intrduce a knwn amunt f adjacent channel interference J at the receiver antenna cnnectr and measure the effect f receiver sensitivity, which is nw. We then have that = F F+ L f J ( ) (2), Where N W is the thermal nise wer in the receiver bandwidth W. lving fr L( f) in we btain J L( f ) = 1Lg 1Lg 1 F (3). The fllwing cmmercial equiment was used: Huawei UMT9 NdeB, GM9 BT, and QUALCOMM dualmde test mbile TM628. Fr the dwnlink, measurements were taken n several different terminals t accunt fr handset cmnent variability. Results are summarized in the tables belw. Table 1 UMT NdeB sensitivity lss due t adjacent channel GMK interference f 2.8 MHz 2.6 MHz 2.4 MHz 2.2 MHz J [m] Table 2 UMT UE sensitivity lss due t adjacent channel GMK interference f 2.8 MHz 2.4 MHz 2.3 MHz 2.2 MHz J [m] Table 3 GM BT sensitivity lss due t adjacent channel WCDMA interference f 2.8 MHz 2.6MHz 2.4 MHz 2.2 MHz J [m] Table 4 GM M sensitivity lss due t adjacent channel WCDMA interference f 2.8 MHz 2.4 MHz 2.3 MHz 2.2 MHz J [m] One can ntice that bth NdeB and UE under test exceeded by several the minimum narrw band blcking erfrmance requirements set frth in [4] and [5]. Fr examle, in [5] the UMT NdeB suffers a sensitivity degradatin f 6 (useful signal level increases frm -121 t -115 m) in the resence f a GMK interfering signal at -47 m and 2.8 MHz frequency ffset. Hwever frm Table 1 ne can ntice that in same cnditins the interference level at the UMT NdeB is -23 m, thus exceeding by 24 the minimum erfrmance secificatin. imilarly, it can be seen that the UMT UE exceeds by 29 the narrw band blcking requirements in [4]. Using Eq.(3) ne can then estimate ulink and dwnlink ACIR. The GM M, UMT UE, GM BT and UMT NdeB receiver nise figures are 9, 8, 3 and 2.1, resectively. Results are ltted in Figure

3 ACI R( ) UMT Ulink 2 GM Ulink 1 UMT Dwnlink GMDwnlink Fr quency f f set ( MHz ) Figure 1 Estimated ACIR Nw that the ACIR is knwn, we can investigate imact f adjacent channel interference n system erfrmance. 3 Mutual Interference and Nise Figure In [1] and [2], netwrk caacity lss is estimated as a functin f ACIR by means f cmuter simulatins. In additin t the imact n caacity, it is als f interest t assess imact f adjacent channel interference n the quality f service f individual users. With that in mind, we nw estimate the receiver nise figure degradatin f a receiver due t an adjacent channel interferer transmitting at wer P and frequency ffset f. Let L be the culing lss between transmitter and receiver. The receiver nise flr will increase by an amunt rrtinal t the interferer transmit wer, and inversely rrtinal t the culing lss and the ACIR. This is reresented by the left hand side f Eq.(4). Rearranging terms we btain the exressin within brackets in Eq.(4) which reresents the receiver effective nise figure F. P + = F L L f ( ) P = F+ = F L L( f) The receiver nise figure degradatin is then F P = 1+ F N W F L L f ( ) (5). (4). Nise figure degradatin is equivalent t sensitivity degradatin,s is als equal t: P 1 + N W F L L( f ) = (6). Numerical results btained by alying Eq.(5)-(6) t the scenaris f interest are resented hereafter. In dwnlink, we use max allwed t evaluate if the actual is accetable. We can get the max allwed is: AllwedMax P = L. (7) where P is the transmitting wer f BT r NdeB f victim system. It can be assumed that dwnlink cverage is nt imacted if the is less than P L, but dwnlink caacity is degraded. One shall remember that the max allwed defined in Eq (7) is rugh estimatin and desn t cnsider the head rm fr wer cntrl. 3.1 Mutual Interference between GM M and UMT NdeB We nw cnsider the mutual interference between GM M and UMT NdeB. We cnsider tw eratin mdes: Crdinated eratin and uncrdinated eratin. Uncrdinated eratin, here, assumes site layut f GM sites at the cell edge f UMT sites as defined in [1]. 1 Crdinated Oeratin In this scenari, the minimum TX wer f GM M is 5m and the maximum wer is 33m because f wer cntrl. M TX wer is determined by culing lss between NdeB and M. M transmitting wer is: P = Min( Max(5m, L + ),33m), where L is the culing lss and is the sensitivity f GM BT. The NdeB in different culing lss is shwn in Figure 2. We can find that UMT NdeB nise flr will increase abut 1.7 when culing lss is equal t 8 and frequency ffset is 2.2 MHz, which will result in increase UE transmit wer and imact UL cverage. In scenaris where cverage is nt a limiting factr, 2.2MHz ffset can give satisfactry erfrmance. If frequency ffset is 2.4MHz, the is less than.2 when culing lss is 8. the interference t UMT Nde B is negligible when frequency ffset is 2.4 MHz. Here, it is assumed GM M transmits at all eight time slts. In ractice, a user ccuies nly ne slt. The effective interference t UMT Nde B is decreased by 9 in this case and the UMT9 is nly.2 at 2.2 MHz ffset. We assume NdeB transmit at full wer, i.e. 43m when cnsider UMT NdeB interference GM M. GM M and the allwed sensitivity degradatin are shwed in Figure 3. We can find that GM M allwed is always larger than

4 actual abut 2. The delta is large enugh t cver the wer cntrl head rm in dwnlink., the NdeB interference t GM M can be tlerated in crdinated eratin when frequency ffset is 2.2MHz UMT NdeB GM BT 2 Uncrdinated Oeratin In uncrdinated eratin, we assume the wrst case scenari in which GM M and UMT NdeB transmit at full wer, i.e., 33 m and 43 m, resectively. ensitivity degradatin vs. culing lss is shwn in Figure 4 and Figure 5. The minimum culing lss (MCL) between UMT NdeB and GM M is assumed t be 8. Frm Figure 4, we can find that the f UMT NdeB is less than.2, which is bviusly accetable, when culing lss is 8 and frequency ffset is 2.6 MHz. We can find frm Figure 5 that the GM M allwed max is always larger than the actual. The max allwed sensitivity degradatin is calculated by assuming maximum culing lss f 12. GM M can tlerate the adjacent inference frm UMT NdeB in uncrdinated eratin scenari when frequency ffset is 2.6 MHz. 3.2 Mutual interference between UMT UE and GM BT imilar t GM M-UMT NdeB mutual interference case, tw eratin mdes are cnsidered: Crdinated eratin and uncrdinated eratin. 1 Crdinated Oeratin The minimum TX wer f UMT UE is -5m and the maximum wer is 21m. UMT UE TX wer is determined by culing lss between GM BT and UMT UE. UMT UE transmitting wer is: P = Min( Max( 5m, L + ),21), where L is the culing lss and is the sensitivity f UMT Nde B. The GM BT fr different culing lss values is in Figure 2. We can find frm Figure 2 that there is n interference imact frm UMT UE t GM ulink with 2.2 MHz frequency ffset. Maximum GM BT wer, i.e. 43m, is assumed when assessing the imact f GM BT interference t UMT UE. Figure 3 shws the max allwed and the actual UMT UE. As can be seen in Figure 3, the max allwed is always larger than the actual value by arund 25.. The delta is large enugh t cver the wer cntrl head rm in dwnlink. it can be cncluded that the interference frm GM BT t UMT UE desn t imact the UMT quality in crdinated eratin when frequency ffset is 2.2MHz. ensitivity Lss [] Culing Lss [] Figure 2 UMT NdeB and GM BT sensitivity degradatin vs. culing lss in crdinated eratin (Frequency ffset 2.2MHz) ensitivity lss [] Culing lss [] GM dwnlink max allwed UMT dwnlink max allwed GM M sensitivity degradatin UMT UE sensitivity degradatin Figure 3 UMT UE and GM M sensitivity degradatin vs. culing lss in crdinated eratin (Frequency ffset 2.2MHz) 2 Uncrdinated Oeratin In uncrdinated eratin, we assume the wrst case scenari in which UMT UE and GM BT transmit at full wer, i.e., 21 m and 43 m, resectively. The MCL between GM BT and UMT UE is 8 and the vs. culing lss is shwed in Figure 4 and Figure 5. Frm Figure 4, we can find GM BT nise flr will increase less than.2 due t the interference frm UMT UE. This is evidently negligible. We can als find frm Figure 5 that the UMT UE allwed max is always larger than UMT UE actual. Maximum culing lss f 12 is assumed when calculating allwed max. UMT UE can tlerate the adjacent channel inference frm GM BT in uncrdinated eratin scenari at 2.6 MHz frequency ffset.

5 ensitivity Lss [] UMT NdeB GM BT Culing Lss [] Figure 4 UMT NdeB and GM BT sensitivity degradatin vs. culing lss in uncrdinated eratin (Frequency ffset 2.6MHz) ensitivity Lss [] Culing Lss [] GM dwnlink max allwed UMT dwnlink max allwed GM M UMT UE sensitivity degradatin Figure 5 UMT UE and GM M nise degradatin vs culing lss in crdinated eratin (Frequency ffset 2.6MHz) Frm [1],we can find the average UMT ulink caacity lss less than 5% when frequency ffset is 2.2MHz ( ACIR=34.5 ) and dwnlink caacity lss less than 1.5%(ACIR=25.5) in rural area with cell range f 5 m in crdinated eratin. The UMT caacity lss and GM utage degradatin are all less than 1% when frequency ffset is 2.6MHz (all ACIR larger than 55 frm Figure 1) in uncrdinated eratin. Frm abve descritin, we can get the fllwing cnclusin:! In crdinated delyment,2.2mhz frequency ffset frm UMT center can be satisfied fr requirement when the eratr can tlerate slight caacity and cverage lss (i.e. UMT9 carrier is allcated 4.2 MHz).! In crdinated delyment, when the eratr has enugh frequency resurce r cannt tlerate abut 1.7 UMT ulink and abut 5% UMT ulink caacity lss, 2.4MHz carrier searatin is needed (i.e. UMT9 carrier is allcated 4.6 MHz).! In uncrdinated delyment, 2.6MHz frequency ffset satisfies the caacity and cverage requirements (i.e. UMT9 carrier is allcated 5. MHz). 5 References [1] 3GPP TR25.816, UMT9 Wrk Item Technical rert, 25. [2]. liman, C. Weathley, Frequency Crdinatin Between CDMA and Nn-CDMA ystems, xxxx [3] 3GPP TR25.942, Radi Frequency ystem cenaris [4] 3GPP T25.11, UE Radi Transmissin and recetin [5] 3GPP T25.14, Base tatin Radi Transmissin and recetin [6] ECC/CEPT, Cmatibility tudy fr UMT Oerating Within the GM 9 and GM 18 Frequency Bands 4 Cnclusins Findings can be summarized in Table 5. Table 5 ensitivity ummary Frequency Offset 2.2MHz 2.6MHz cenari Crdinated Uncrdinated UMT NdeB NF GM BT NF UMT UE NF GM BT NF allwed by ~25 allwed by ~2 allwed allwed