Lecture 3: Evolved RAN and Radio Link Budget

Transcription

1 Lecture 3: Evolved RAN and Radio Link Budget ELEC-E7230 Mobile Communications Systems Edward Mutafungwa, 2015 Department of Communications and Networking

2 Outline Background Motivation, requirements, RAN architecture Long-Term Evolution (LTE) LTE downlink and uplink PHY LTE radio protocols and channels LTE Radio Resource Management LTE-Advanced LTE-Advanced carrier aggregation LTE-A relaying CoMP and extended MIMO Principles of Radio Link Budget (RLB) LTE RLB Some details on RLB (powers, path loss, shadowing etc.) Link Budget Examples

3 1- LTE-Advanced Carrier Aggregation (Rel.10/11)

4 Background Some key requirements for LTE-Advanced 1 Gbps on the downlink and 500 Mbps on the uplink. Higher peak and average spectral efficiencies than in LTE Rel. 8 More homogeneous distribution of the user experience over the coverage area. Backward compatibility to LTE Rel. 8

5 1.1 Principles of Carrier Aggregation

6 Principle The LTE-Advanced target peak data rate of 1 Gbps in downlink and 500 Mbps in uplink can be achieved with bandwidth extension from 20 MHz up to 100 MHz. In LTE-Advanced this extension is achieved through carrier aggregation By combining N LTE Release 8 Component Carriers (CC), together to form N x LTE bandwidth, up to 5 x 20 MHz = 100 MHz operation bandwidth could be obtained Component carrier (CC) LTE-Advanced maximum configuration R8 20 MHz R8 20 MHz R8 20 MHz RF band R8 20 MHz R8 20 MHz Frequency

7 Backward compatibility with Rel.8/9 LTE Rel.8/9 terminals can receive/transmit only one component carrier LTE-Advanced terminals may receive/transmit on multiple component carriers (CCs) simultaneously to reach higher data rates. R8/9 UE LTE-A UE 1.4MHz 20MHz R8/9 UE R8/9 UE R8/9 UE Frequency 7

8 Example LTE Rel. 8/9 frequency bands Band Uplink (MHz) Downlink (MHz) Region Europe, Asia Europe, Asia, Americas Americas, Korea, Europe, Asia, Canada, Korea Europe. Japan, Latin America Americas, Verizon For more, see:

9 Carrier Aggregation types Intra-band, contiguous CA Band 1 Band 2 Intra-band, non-contiguous CA Frequency Band 1 Band 2 Inter-band, non-contiguous CA Frequency Band 1 Band 2 Frequency 9

10 Contiguous vs non-contiguous CA Rel-8/9 backward compatible carriers are the basic building blocks For an LTE Rel.8 terminal, each component carrier will appear as an LTE carrier, while an LTE-Advanced terminal can use the total aggregated bandwidth R8/9 UE LTE-A UE 1.4MHz 20MHz R8/9 UE R8/9 UE R8/9 UE Frequency

11 Contiguous vs non-contiguous CA In terms of UE complexity, cost, capability, and power consumption, it is easier to implement contiguous CA with minimal changes to the physical layer structure of Rel.8-9 LTE. In non-contiguous CA advanced RF components are needed in receiver in order to receive non-adjacent carriers. Compared to non-contiguous CA, it is easier to implement resource allocation and management algorithms for contiguous CA.

12 Contiguous vs non-contiguous CA In practice it seems that in the low frequency band (< 4 GHz) it will be difficult to allocate continuous 100 MHz bandwidth for a mobile network. The non-contiguous CA technique provides a practical approach to enable mobile network operators to fully utilize their current spectrum resources Thus, to use also currently unused scattered frequency bands and those already allocated for some legacy systems, such as GSM and 3G systems.

13 UE categories for CA 3GPP specifies UE categories for placing devices into specific segments according to combined DL and UL capabilities (MIMO, modulation level, CA etc.) Categories 1-5 where specified for LTE Rel. 8 Categories 6-10 specified for LTE-Advanced (Rel. 10 and later) UE Category Carrier Aggregation 3GPP Release Category 6 Category 7 Category 8 Category 9 Category MHz DL 1 20 MHz UL 2 20 MHz DL 2 20 MHz UL 2 20 MHz DL 2 20 MHz UL 3 20 MHz DL 1 20 MHz UL 3 20 MHz DL 2 20 MHz UL Release 10 Release 10 Release 10 Release 11 Release 11

14 Current CA status: networks

15 Current CA status: devices Example Cat. 9 device Example Cat. 6 devices

16 1.2 Practical configurations and deployment issues

17 Practical CA combinations and naming conventions The following terms and definitions for CA combinations are applied: Aggregated Transmission Bandwidth Configuration (ATBC): This refers to the number of aggregated resource blocks. CA bandwidth class (A, B and C): Refer to the combination of ATBC and number of CCs. In Rel.10 and Rel.11 classes are: Class A: ATBC 100, maximum number of CC = 1 Class B: ATBC 100, maximum number of CC = 2 Class C: 100 < ATBC 200, maximum number of CC = 2 CA configuration: This defines the combination of operating bands and CA bandwidth class, for examples configurations, see the next slide Bandwidth (B) 1.4MHz 3 MHz 5MHz 10MHz 15MHz 20MHz Resource Blocks (N rb )

18 CA configuration examples (FDD) Type of CA Intra-band, contiguous (*) Intra-band, contiguous (**) CA configuration Max bandwidth Max number of CC s CA_1C 40MHz 2 CA_7C 40MHz 2 Inter-band (*) CA_1A_5A 20MHz 1+1 Inter-band (**) CA_3A_5A 30MHz 1+1 Intra-band, noncontiguous (**) (*) Rel.10; (**) Rel.11 CA_25A_25A 20MHz 1+1

19 CA configuration examples (FDD) Example: Configuration CA_1C means that CA operate on Band 1, with two continuous components carriers, with a maximum of 200 RBs. Source: 4G Americas, 2014

20 Interesting CA deployment scenarios The coverage areas of component carriers (CCs) can be different Example 1: Large frequency separation between CCs Interesting CA scenario occurs when operator uses e.g. 2GHz and 800MHz bands for LTE (CA_1A_5A) Load balancing between CCs will not be trivial due to traffic variations within coverage areas of different CCs CA not utilised in areas where CC bands coverage do not overlap enodeb 800MHz + 2GHz CA 800MHz No CA

21 Interesting CA deployment scenarios Example 3: Antenna directions are not the same for all CCs enodeb Example 4: CA possible if the same enodeb is controlling main antenna unit and remote radio head (RRH) enodeb RRH

22 1.3 Primary and secondary Component Carriers

23 Primary and secondary CC When UE first establishes RRC connection with enodeb, only one CC is attached for downlink and uplink directions. Corresponding CCs are called as primary CCs (PCCs) for both downlink and uplink, and the related cell is the primary serving cell (PCell). Based on the traffic load and QoS requirements, UE can be attached with additional one (or more) CC, called as secondary CC (SCC) which correspond to the secondary serving cell (SCell).

24 Primary and secondary CC The use of downlink/uplink SCC is decided by the enodeb. The PCC/SCC configuration is UE-specific and can be different for different UEs served by the same enodeb. Band 1 Band 2 CC1 CC2 CC3 PCC SCC PCC SCC PCC Frequency

25 Primary and secondary CC The PCC serves as an anchor CC for the user and it is used for basic connectivity functionalities The SCCs carry only user data and dedicated signaling information PDSCH (physical DL shared channel), PUSCH (physical UL shared channel), and PDCCH (physical DL control channel) Since user connection greatly depends on PCC, it should be robust in both downlink and uplink PCC should be selected such that it provides ubiquitous coverage and/or best overall signal quality When UE is moving within the enodeb service area the PCC may be changed CC with best signal quality Load balancing carried out between CCs

26 1.4 Radio Resource Management principles for Carrier Aggregation

27 Radio Resource Management in CA Based on user QoS requirements and traffic load, the enodeb assign a set of CCs for user and physical layer scheduling is carried out over multiple users on each CC. Cross-carrier scheduling is also possible In cross-carrier scheduling PDCCH is transmitted from a particular CC and may contain the scheduling information on other CCs as well as its own CC.

28 Radio Resource Management in CA Admission control is performed as in LTE by the enodeb before establishing new radio bearer(s) Link adaptation and HARQ are carried out per CC Cross-carrier scheduling Packet scheduling Admission control L3 operations Packet scheduling LA, HARQ L1 (PHY) LA, HARQ L1 (PHY) CC 1 CC 2

29 Radio Resource Management in CA To keep CA compatible with Rel.8/9 independent layer 1 transmissions are executed in CCs Each component carrier has its own transmission parameters (e.g., TX power, modulation and coding schemes, and MIMO configuration) in PHY The downlink SCCs can be dynamically activated and deactivated => power consumption optimization in UE Cross-carrier scheduling Packet scheduling Admission control L3 operations Packet scheduling LA, HARQ L1 (PHY) LA, HARQ L1 (PHY) CC 1 CC 2

30 2. LTE-Advanced Relaying 2/19/2010 Word template user guide 30

31 2.1 Relaying principles, need for relaying and use cases 2/19/2010 Word template user guide 31

32 Wireless relay: Principle Repeaters (amplify and forward relays) are well known and used in 2-3G networks. I have a message I listen, modify and retell I am only listening Base Station (BS) Relay Station (RS) Mobile Station (MS) The rest of this lectures considers mainly relays that detect, encode and retransmit (decode and forward) a signal between base station and terminal

33 Why relays for LTE? Some key requirements for LTE-Advanced 1 Gbps on the downlink and 500 Mbps on the uplink. Higher peak and average spectral efficiencies than in LTE Rel 8. More homogeneous distribution of the user experience over the coverage area. Expected properties of LTE- Advanced relays Enhanced capacity in hotspots. Enhanced cell coverage. Overcome extensive shadowing. Enable more homogenous user experience. Low total cost of operation (TCO).

34 Proposed benefits from relaying Relay link Access link UE Increase RN throughput in hotspots UE Direct link UE UE d-enb RN Extend coverage RN Overcome excessive shadowing

35 But are relays really needed? Claim is that relays will provide an easy and cost effective way to increase macrocell range, fill coverage holes in macrocells and improve indoor coverage. Counter argument: There are other efficient solutions like small cells (micro, pico cells etc.) Value proposition: Relays are self-backhauled wireless nodes (no wired or dedicated fixed wireless backhaul) and thus flexible to deploy Self-backhauling implies that backhaul is provided my the macro base station directly

36 Conventional small cells Source: Small Cell Forum

37 Use cases for LTE-Advanced relays Relay use case Fixed Infrastructure Usage Temporary Usage Outdoor Relay for Indoor Coverage Enhancement In-Building Relay for Coverage Enhancement Coverage in case of emergency /disaster Coverage in case of events Mobile Usage Coverage in trains, busses, ferries This has not realized in Rel.10/11

38 2.2 LTE-Advanced relaying principles

39 LTE-Advanced relaying principles In 3GPP Technical Report [TR ] the following has been stated: Relaying is considered for LTE-Advanced as a tool to improve e.g. the coverage of high data rates, group mobility, temporary network deployment, the cell-edge throughput and/or to provide coverage in new areas. LTE-A specifications support fixed relaying and nomadic relaying is possible but relay (group) mobility is not yet part of the standards. The relay node is wirelessly connected to the radio-access network via a donor enode B. Relay-eNB link Donor cell border Donor enb Relay Node (RN)

40 Inband operation/outband operation Inband operation (RN-UE and enb-rn links on same carrier frequency) UE UE-eNB (direct) link Donor enb RN-eNB (relay) link Relay Node (RN) Donor cell border RN-UE (access) link UE Outband operation (RN-UE and enb-rn links on different carrier frequency) UE-eNB link RN-eNB link Donor cell border RN-UE link UE Donor enb Relay Node (RN) UE Note: In outband operation RN-UE link do not need to be LTE Rel 8 compatible if Rel 8 terminals are not operating on this frequency carrier.

41 3GPP relay nodes 3GPP Type 1 relay nodes are an inband RNs Assigned a unique physical-layer cell identity (PCI) Implements same Radio Resource Management mechanisms (scheduling, admission etc.) like a enode B Backward compatibility: support also LTE Rel-8 UEs (to UE RN appears just like any other Rel. 8 enode B) To LTE-Advanced UEs, it is possible for a relay node to appear differently than Rel-8 enodeb to allow for further performance enhancement Donor enb control resources in enb relay link Donor enb Type 1 RN UE Relay control cell of its own: protocol terminations done mostly in RN

42 3GPP relay nodes Type 1a relays: Type 1a relays characterised by the same set of features as the Type 1 relay node, except that Type 1a operates outband Type 1b relays: Type 1b are in same featues and inband like Type 1 but transmission in relay (DeNB-RN) and access (RN-UE) link occur at same time => high antenna isolation required (expensive) Type 1 transmissions in relay and access links are time-division multiplexed Source: O. Bulakci, NSN, 2011

43 3GPP Type 2 relay In 3GPP Technical Report [TR ] A Type 2 relay node was defined to be an inband relaying node characterized by the following: It does not have a separate Physical Cell ID and thus would not create any new cells. It is transparent to Rel-8 UEs; a Rel-8 UE is not aware of the presence of a Type 2 relay node. Yet, up to date such relay type has not been standardized for LTE. 2/19/2010 Word template user guide 43

44 2.3 LTE-Advanced Type 1 relaying: The Backhaul problem

45 Inband Type 1 relaying: the resource sharing needed between links In order to allow inband relaying, resources in the LTE time-frequency space needs to be shared between backhaul and access links Backhaul link between RN and Donor enodeb: The name of this logical interface is Un (defined in LTE Rel.10) Backhaul resources cannot be used for the access link. The name of this logical interface is Uu (as in LTE Rel. 8). Un Uu Donor enb Relay Node (RN) UE Resource sharing should be compatible with LTE Rel 8

46 Resource sharing: General principle General principle for resource partitioning at the LTE- Advanced Type 1 relay: enb RN and RN UE links are time division multiplexed in a single carrier frequency RN enb and UE RN links are time division multiplexed in a single carrier frequency DL (Donor) enodeb RN RN UE UL UE RN RN (Donor) enodeb Sounds simple but is it really straightforward?

47 BH backward compatibility: A problem Backward compatibility requirement with LTE Rel.8 creates a problem: Rel.8 UE expects continuous pilot/control transmission in DL from enodeb. In case of Type 1 relay, RN represents the enodeb for Rel.8 terminal. RN should be able to receive backhaul (Un) transmissions on the same frequency. Problem: Reception and transmission on the same frequency carrier is possible only for Type 1b relay that requires physical separation (strong isolation) between RX and TX antennas. Yet, this is costly solution. Type 1 relaying is the most attractive relaying option. Yet, due to above problem there was a threat in the beginning of the LTE- Advanced standardization that relaying will be dropped out.

48 BH backward compatibility: The solution Recall: LTE Frame consists of 10 subframes of 1 ms each. Actually part of the LTE DL subframes can be configured as MBSFN subframes MBSFN refers to term Multi-Media Broadcast over a Single Frequency Network. In LTE Rel.8 MBSFN subframes are designed to carry MBMS (Multimedia Broadcast Multicast System) information. MBMS service area typically covers multiple cells. Example application is Mobile TV. The set of MBSFN subframes is semi-statically assigned; a maximum of 6 subframes can be configured out of the subframes 1, 2, 3, 6, 7, and 8 [*]. # 0 # 1 # 2 # 9 10 ms frame with 10 1ms subframes How could this be leveraged?

49 BH backward compatibility: The solution MBSFN subframes used for the DeNB-RN link (Un interface) Non-MBSFN subframes from DeNB used for UE directly connected to DeNB MBSFN subframes not used in RN-UE link (they are subframes) RN uses its non-mbsfn subframes for UEs it serves DeNB subframes # 0 # 1 # 2 # 9 Donor enb Un RN Uu UE # 0 # 1 # 2 # 9 RN subframes

50 3. Coordinated Multipoint (CoMP) Transmission and Receiption 2/19/2010 Word template user guide 50

51 3.1 CoMP: Idea and benefits 2/19/2010 Word template user guide 51

52 Idea of CoMP Coordinated Multi-Point Transmission is one of the most important technical improvements of LTE Rel.11 CoMP improves to some extent macrocell network performance Through reduced interference (increased signal to interference and noise ratio, SINR) In case of Heterogeneous Network (HetNet) composed by macrocells, microcells and picocells, CoMP is especially useful High-power macrocells overlapping coverage with low-power small cells

53 Idea of CoMP In all network deployment strategies (macrocell only and HetNet) cell edge users are experiencing the inter-cell interference. Downlink: Inter-cell interference occurs due to parallel transmissions from adjacent base stations Uplink: Intercell interference occurs due to simultaneous transmission (on the same time-frequency resources) by users in adjacent cells. The goal of the CoMP is to further minimize inter-cell interference for cells that are operating on the same frequency enb 1 UE 1 in cell center Strong signal from serving BS (enb1), weak interferer (enb2) UE 2 at cell edge Weak signal from serving BS (enb1), strong interferer (enb2) UE 1 UE 2 enb 2

54 3.2 CoMP scenarios 2/19/2010 Word template user guide 54

55 3GPP Rel.11 CoMP scenarios 3GPP Rel.11 standardization is based on four different CoMP scenarios. All scenarios assume Ideal Backhaul Non-ideal backhaul scenarios considered only in Release 12 Rel. 12 also considers inter-site CoMP scenarios Scenario 1: Homogeneous network with intra-site CoMP Scenario 3/4: Network with low power RRHs or small cells within the macrocell coverage (in scenario 3 macro and smalls employ different cell IDs, while they are same for scenario 4) enb Coordination area enb Low Tx power RRH (Omni-antenna) Optical fiber High Tx power RRH Optical fiber Scenario 2: Homogeneous network with high Tx power (sectored) RRHs

56 CoMP terminology CoMP Cooperating Set The CoMP Cooperating Set is is a set of geographically separated TX/RX points that are directly or indirectly involved in data transmission to a device in a time-frequency resource The CoMP cooperating set defines the coordination area CoMP Measurement Set The CoMP Measurement Set is a set of points, in which channel state information (CSI) or statistical data related to their link to the mobile device is measured and/or reported 2/19/2010 Word template user guide 56

57 3.3 CoMP categories and schemes 2/19/2010 Word template user guide 57

58 General CoMP categories Joint processing: Joint processing occurs where there is coordination between multiple TX/RX entities that are simultaneously transmitting or receiving to or from UEs. Coordinated scheduling or beamforming: This category is often referred to as CS/CB (coordinated scheduling / coordinated beamforming). It is a form of coordination where a single TX/RX point operates at the time. However the communication is made assuming an exchange of control data among several coordinated entities. To apply either of these modes, fast channel feedback is required so that the transmission parameter changes can be made. The techniques used for CoMP are different for the uplink and downlink. This results from the fact that the enbs are in a network, connected to other enbs, whereas the handsets or UEs are individual elements 2/19/2010 Word template user guide 58

59 Downlink CoMP DL CoMP Joint Processing Coordinated scheduling/beamforming Joint Transmission Dynamic Point Selection Joint Transmission (JT): Transmission executed from multiple points at a time (within CoMP cooperating set) Dynamic Point Selection (DPS): Transmission executed from one point at a time (within CoMP cooperating set). Also known as dynamic cell selection Coordinated scheduling/beamforming: Data to a UE is transmitted from one transmission point. The scheduling decisions as well as transmission beams are coordinated to control the interference Word template user guide 2/19/

60 Downlink CoMP Joint processing schemes for transmitting in the downlink: Improve the received signal quality and strength. Actively cancel the interference from transmissions that are intended for other UEs. This form of CoMP places a high demand onto the backhaul network because the copies of same data need to be sent to each transmission point that will be transmitting it to the UE. Coordinated scheduling and or beamforming : Backhaul requirements are reduced since only scheduling decisions and details of beams needs to be coordinated between multiple transmission points Relatively lower SINR gains compared to joint processing schemes (particularly on cell edge)

61 Uplink CoMP UL CoMP Joint Reception Coordinated scheduling Joint Reception: Antennas at different reception points are utilized. Coordinating between the different reception points it is possible to form a virtual antenna array. The signals received by the reception points are then combined and processed to produce the final output signal. The main disadvantage with this technique is that large amounts of data needs to be transferred between the reception points Coordinated scheduling: This scheme coordinates the scheduling decisions amongst the reception points to minimize interference This scheme provides a reduced load in the backhaul because only the scheduling data needs to be transferred between the different reception points that are coordinating with each other. Receiver processing in centralized reception point Word template user guide 2/19/

62 3.4 LTE-Advanced extended Multiple Input Multiple Output (MIMO) 2/19/2010 Word template user guide 62

63 Benefits of multi-antenna techniques The availability of multiple antennas at the transmitter and/or the receiver may achieve different aims: Provide additional diversity against fading on the radio channel Can be used to shape the antenna beam (beamforming) in a certain way e.g. to maximize the overall antenna gain in the direction of the target receiver or transmitter Spatial multiplexing by enabling transport multiple data streams that within the same limited channel bandwidth Source: M. Sauter, From GSM to LTE : an introduction to mobile networks and mobile broadband, 2011

64 Downlink MIMO Downlink MIMO schemes are extended/enhanced from Rel.8 LTE Operation is extended to support 8 TX antennas, (instead of 4TX supported by Release 8 LTE). LTE Rel.8 Peak data rate DL 300 Mbps (4x4 MIMO, 20 MHz) LTE-A target 1 Gbps (8x8 MIMO, MHz) Peak spectral efficiency DL 15 bps/hz 30 bps/hz

65 Spectral efficiency [bits/s/hz] Spectral efficiency improved by MIMO Max SE Max SE SIMO (1x2) MIMO (2x2) MIMO (4x4) MIMO (8x8) SINR [db]

66 Uplink MIMO Uplink single-user MIMO is being introduced in order to increase average user throughput and, in particular, user throughput at the cell edge UL SU-MIMO was considered already for Rel.8 LTE, but compared to the added benefit, it was found too expensive for the terminals due to need of multiple power amplifiers. Up to 4 TX antenna transmission can be used in LTE- Advanced uplink.

67 CoMP is actually a MIMO variant. In CoMP transmitters are not necessarily co-located But linked by a high speed connection and can share user data In CoMP transmission if coherent combining used it also known as cooperative or network MIMO Ref: Agilent

68 Radio Link Budget (RLB)

69 Network Planning Our focus area 150 Network planning consists of 3 phases: - Dimensioning, detailed planning and optimization Dimensioning Note: We omit core network Path Loss [db] Distance from BS [km] + EIRP 58dB Margins 23dB Sensitivity -100dB Allowed PL 135 db 1000 x 5000 x Area and propagation information Radio Link budget # Network elements Detailed planning Input from dimensioning TX power 43dBi Antennas 2 Antenna tilt 5 o Parameter x, y, z Network planning tools System simulations BS + RS Configurations and topology plan Optimization + Operating network (drive tests, monitoring) Optimized system

70 1. Principles of RLB

71 Background Radio Link Budget (RLB) is a basic tool in radio engineering. It is used to compute estimates for e.g. Received power in terminal/enodeb Can be used to estimate user rates Allowed propagation loss Connection range between transmitter and receiver RLB take into account the gains and losses from the transmitter, the communication medium (wireless channel in our case) and the receiver. Typical parameters are related to the propagation model (radio environment), antennas (antenna directivity/gains), feedlines (cable attenuation) and the receiver properties (product specific sensitivity, noise figure)

72 Example: RLB in LTE cell coverage estimation LTE enodeb with 3-sector transmission User on the distance where minimum required rate can be provided assuming a certain load. Example: We require that user should reach 1Mbit/s data rate when 10% of the cell resources are allocated for him/her. Question: How far from enodeb user can be? This distance gives cell range under above constraint

73 Simplified RLB EIRP = Effective Isotropic Radiated Power, contains transmitted power and antenna gain Transmitter characteristics Channel characteristics Receiver characteristics Number that is used to estimate the cell range BS Transmitter BS to MS Total transmission power 43 dbm (20 W) Transmitter antenna gain 15 dbi EIRP 58 dbm Margins Shadow fading margin 7 db Interference margin 4 db Penetration loss 10 db Total Margin 21 db UE Receiver (Max coverage) Receiver sensitivity dbm System gain db Allowed Propagation Loss db

74 Simplified RLB: Terminology dbi = db(isotropic). It is the forward gain of a certain antenna compared to the ideal isotropic antenna which uniformly distributes energy to all directions. dbm = db(1 mw) is a measured power relative to 1 mw (e.g. 20W is 10*log(1000*20)= 43 dbm Effective isotropic radiated power is the amount of power that would have to be emitted by an isotropic antenna (that evenly distributes power in all directions and is a theoretical construct) to produce the peak power density observed in the direction of maximum antenna gain. EIRP can take into account the losses in transmission line and connectors and includes the gain of the antenna.

75 RLB through equations In this case the Allowed Propagation Loss (APL) can be calculated as follows: APL = EIRP- min{ P RX }- M Total = P TX +G A - min{ P RX }- M SF - M I - M Penetration Here min{ P RX } = Receiver sensitivity [dbm] P TX = Transmission power in BS [dbm] G A = BS antenna gain [dbi] M SF = Shadow fading margin [db] M I = Interference Margin [db] M Penetration = Indoor penetration loss [db] Penetration loss simply depends on the expected building wall losses.

76 The RLB principle TX/RX parameters Data rate requirement User resource allocation Link budget Allowed propagation loss Path loss model System range TX/RX parameters depend on the network deployment Equipments (enodeb, UE, antennas), site properties Data rate requirement Depends on the service Data rate can be mapped to required signal to interference and noise ratio (SINR) User resource allocation Traffic expectations Path loss model Environment/clutter type 76

77 2. LTE Downlink Radio Link Budget

78 78 LTE Downlink RLB In the following we go through this LTE downlink radio link budget in details This is a snapshot from excel tool that is given for participants There will be some solved examples discussed later.

79 Resource allocation and rate requirements Parameter Number of PRBs Data rate Comment This is estimated by assuming the operation bandwidth and number of users served at the same time. In case of 10MHz band we have 50 resource blocks (48 for data). Then 10PRB takes 10/48 of all resources In this case we assume 2Mbits/s target rate

80 Remark on rate requirement In case of constant bit rate service (like real time video) the 2Mbits/s requirement defines how much resources user continuously employs In usual case (e.g. web browsing, file downloading, streaming video) the data transfer happens in bursts so instantaneous rate can be high while there are time gaps between transmissions for user (time multiplexing of users) Example: If user on cell edge download 1 Mbit file (s)he needs round 0.1 seconds for all 48 PRBs OR (s)he is given 5PRBs for 1 second time period Other options of course are possible as well

81 Transmission characteristics Parameter enodeb TX power Comment Typical value is 20W-60W (43dBm-48dBm) 20W on 5MHz band (as in WCDMA/HSPA) 40W on 10MHz band (most usual test case for Rel.8 LTE) 60W on 20MHz band Antenna gain Cable loss EIRP Typical 1.3 m high panel antenna at 2 GHz band gives 18 dbi gain in main direction Loss between the enodeb antenna and the low noise amplifier. The cable loss value depends on the cable length, cable type and frequency band. EIRP = TX power + antenna gain cable loss

82 UE receiver (1/2) Parameter UE Noise Figure (NF) Thermal Noise Receiver Noise Floor Comment NF measures of degradation of the SNR by the components in the RF receiver chain, product specific. Typical values: 6-11dB Thermal noise = Boltzmann constant x T (Kelvin) x Effective bandwidth. Here Boltzmann constant = 1.38 x 10^(-23) J/K (J = Ws) Reference temperature 20 Celsius = 290 Kelvin Effective bandwidth = Number of PRB s x 180kHz Receiver noise floor = UE NF + Thermal noise

83 UE receiver (2/2) PHICH = Physical HARQ Indicator Channel PBCH = Physical Broadcast Channel PDCCH = Physical DL Control Channel Parameter SINR Receiver sensitivity Control channel overhead RX antenna gain Comment Required Signal to Interference and Noise Ratio depends on the data rate, number of PRBs and link efficiency. We consider this in more details later in this slide set Minimum required power in receiver required to detect the signal. Receiver sensitivity = Receiver Noise Floor + SINR Control channel overhead includes the overhead from reference signals, PBCH, PDCCH and PHICH. 5%-25% leads to 1dB-4dB overhead. Depends on the receiver antenna, usually 0dBi for handheld terminals

84 Margins and losses Parameter Body loss Shadowing loss Interference margin Indoor penetration loss Comment Body loss is typically included for voice link budget where the terminal is held close to the user s head. 3-5dB for voice. Depends on the propagation environment. Typical values: 4-7dB. Interference margin accounts for the increase in the terminal noise level caused by the other cell interference. If we assume a minimum G-factor of 4 db, that corresponds to 5.5dB IM (10*log10(1+10^(4/10)) = 5.5 db). Typical values for IM: 3dB 8dB. Depends on the building types. In urban area 20dB, in suburban/rural area with light buildings 10dB.

85 Allowed propagation loss APL = P TX +G A(NodeB) - L Cable +G A(UE) - min{ P RX } - M SF - M I - L C - L body - L Penetration

86 Carrier Aggregation RLB example

87 RLB example on different component carrier coverage areas Assume the link budget parameters below, 10MHz band, 800MHz/2GHz component carriers, 35 meter base station antenna height and 1.5 meter UE height. Compute the coverage Radio in case Communication of large city for 2Mbps Systems service II, Exercise when enodeb 3, 2014 allocates 4 PRBs for the user (12 users/cell served simultaneously). Coverage area for 800MHz carrier Problem 1. LTE downlink RLB (excel in Noppa): Assume the following l 2.1GHz carrier, Coverage 25 meter area base for 2GHz station carrier antenna height and 1.5 meter UE hei enodeb Parameter BS TX power BS antenna gain BS cable loss UE noise figure Interference margin RX antenna gain RX body loss Control channel overhead Indoor penetration loss Shadow fading margin BS antenna configuration Value 40W 18dBi 2dB 7dB 4dB 0dBi 0dB 1dB 20dB 7dB 2x2/4x4 MIMO

88 RLB example on different component carrier coverage areas 2GHz component carrier: Indoor user maximum distance from enodeb = 300 meters Outdoor user maximum distance from enodeb = 1130 meters 800MHz component carrier: Indoor user maximum distance from enodeb = 730 meters Remarks: If network coverage planning has been done assuming 800MHz carrier and indoor users, then 2GHz CC outdoor coverage is even larger than 800MHz CC coverage. Thus, indoor users close to enodeb and outdoor users in the whole cell can be scheduled to 2GHz CC

89 RLB example on different component carrier coverage areas Indoor coverage area for 800MHz carrier Indoor coverage area for 2GHz carrier Overlapping 800MHz indoor coverage and 2GHz outdoor coverage 89

90 Thank You! Slides originally prepared by Prof. Jyri Hämäläinen 90

91 Additional Slides 91

92 4. DL Link Budget Examples

93 Urban area example (DL) Assume the link budget parameters below, 10MHz band, 2GHz carrier, 35 meter base station antenna height and 1.5 meter UE height. Radio Communication Systems II, Exercise 3, 2014 Compute the coverage in case of large city for 2Mbps service when enodeb allocates 4 PRBs for the user (12 users/cell served simultaneously). What Problem happens 1. for LTE the service downlink coverage RLB if enodeb (excel can in Noppa): allocate all Assume available 48 the PRBs following for this user link b (target 2.1GHz rate being carrier, the same 25 meter 2 Mbps)? base station antenna height and 1.5 meter UE height: Increase the user rate 5Mbps and solve problem again Parameter Value BS TX power 40W BS antenna gain 18dBi BS cable loss 2dB UE noise figure 7dB Interference margin 4dB RX antenna gain 0dBi RX body loss 0dB Control channel overhead 1dB Indoor penetration loss 20dB Shadow fading margin 7dB BS antenna configuration 2x2/4x4 MIMO

94 Results Case 2Mbit/s and 48 PRB s: Range in large city = 880 meters Range in suburban area = 2.0 km Case 5Mbit/s and 4 PRB s: Range in large city = 110 meters Range in suburban area = 240 meters Case 5Mbit/s and 48 PRB s: Range in large city = 650 meters Range in suburban area = 1.5 km Case 2Mbit/s and 4 PRB s: Range in large city = 300 meters Range in suburban area = 680 meters

95 Remark on range (1/3) Question: We increase the amount of radio resources 12 times (4 PRB ->48 PRB) but range is not increasing directly proportionally. Why range increase is so small? Answer: If more PRB s are used, less data needs to be loaded per PRB => SE and accordingly SINR requirement decreases In 2Mbit/s case SINR requirement decreases from 8.8dB to -7.5dB, the difference being 16.3dB (see next slide) In 5Mbit/s case SINR requirement decreases from 24.2dB to -2.8dB, the difference being 27.0dB (see next slide) This increases allowed propagation loss with same amounts. Yet, if distance from/to enodeb is short, then the path loss increases fast as a function of distance (see next slides)

96 Spectral efficiency [bits/s/hz] Remark on range (2/3) LTE 2x2 MIMO maximum spectral efficiency (7.5bits/s/Hz) 7 SISO Spectral Efficiency MIMO Spectral efficiency (2x2) 3 2 Shannon AWGN bound (SISO) SINR [db]

97 Remark on range (3/3) 16.3dB 27.0dB

98 Other remarks In 4 PRB case we can serve 12 users at the same time while in 48 PRB case we can serve only single user. Range extension by using more resources per user can take place only when cell load is low. User usually needs 2-5Mbit/s rates just during very short time periods In e.g. web browsing/streaming video data is transferred in bursts. Thus, if instantaneous rate is high, user will have good use experience.

99 Okumura-Hata Path loss Model 99

100 Okumura-Hata Model (1) (Okumura-) Hata model is one of most common models for signal prediction in large macrocells This model exists in many version, and is defined for limited ranges of parameters Originally, this model is valid for: Distances: km Frequency ranges: MHz (it was extended later) 100

101 Okumura-Hata Model (2) Okumura used extensive measurements of base station-tomobile signal attenuation in the city of Tokio (Japan) He developed a set of curves that gives the median attenuation (relative to free space) of signal propagation in irregular terrain The base station heights for these measurements were m The Hata model is an empirical formulation of the graphical path-loss data provided by Okumura (model is isotropic) Closed-form formulas provided by Hata simplify path loss calculations (four different environments were defined) 101

102 Environment factor Relative attenuation The original Okumura Okumura model provides the median value for the average path loss attenuation Effective antenna height hte G( hte) 20 log 30m hte 1000m 200 hre G( hre) 10log hre 3m 3 hre G( hre) 20log 3m hre 10m 3 L ( ), 50 db L A f d G h G h G F mu te re Area L F = free space attenuation 102

103 Okumura-Hata Model (3) The original Hata model is given by where the parameters (and their corresponding units) are 150 and 1500 MHz

104 Okumura-Hata Model (4) The correction factor for the mobile antenna height a i (h MS ) depends on the size of the coverage area: Large/dense city (i.e., i = 1 ), Medium/small size city (i.e., i = 2 ), Suburban area (i.e., i = 3) and rural/open area (i.e., i = 4 )

105 Okumura-Hata Model (5) Correction factor for the mobile antenna height (cont d)

106 Okumura-Hata Model: PL vs. Range (1) Carrier frequency 106

107 Okumura-Hata Model: PL vs. Range (2) Carrier frequency 107

108 Okumura-Hata Model: PL vs. BS Antenna Height Carrier frequency 108

109 Okumura-Hata Model (6) In mobile communication systems (like GSM and 3G), base station antennas are rarely placed on locations over 40 meters in height Systems like television and radio broadcasting may use towers that higher than 100 meters The height of the FM- and TV-mast (Helsinki-Espoo) located in Latokaski (Espoo), has a current height of 326 meters (third highest structure in Finland) In the next slide, we illustrate the impact of the environment type in the path loss attenuation It is found that difference between large and medium size cities is small, while Path loss attenuation in suburban and open areas is far more smaller than in city environments

110 Okumura-Hata Model: PL vs. Range (3) Environment Type 110

111 Okumura-Hata Model (7) Later on, Okumura-Hata model was extended to the MHz frequencies, in the COST 231 research program The distance interval was also extended ITU-R sector adopted this model in Recommendation P.529 where MS antenna height correction factor is the same as in the previous model, and the additional term is given by

112 Okumura-Hata Model (8) Finally, an extension to the Okumura-Hata model for distances between km is given by the expression where the β parameter is given by Note: The COST 231 extension of the Okumura-Hata model is a single slope model for distances in the range of 1-20 km

113 Remark on path loss models Okumura-Hata model represents the most well-know macrocell model Walfisch-Ikegami model is an other well-known model for urban area In network planning tools above-mentioned models are used with additional clutter corrections Several different clutter types can be defined with different additional db/m loss factors Planning tool design companies are usually not publishing all their models There are also several models for small outdoor and indoor cells Yet, the smaller are the cells, the worse are the isotropic models that don t take into account the environment (e.g. building) structure. When high carrier frequency communication take place in cellular systems (5G) ray tracing models become more important. 113