Resource sharing in LTE‐Advanced relay networks: uplink system performance analysis

Abstract

Relay-enhanced networks are expected to fulfil the demanding coverage and capacity requirements in a cost-efficient way. Type 1 inband relaying has been standardised as an integral part of the Third Generation Partnership Project (3GPP) Long-Term Evolution Release 10 and beyond (LTE-Advanced). This type of relay nodes (RNs) supports a relaying mode where the RN to donor evolved node B (donor eNB, DeNB) link (relay link, a.k.a. backhaul link) transmission is time-division multiplexed with the RN-served user equipments (RUEs) to RN link (access link) transmission, whereas macrocell-served user equipments (MUEs) share the same resources with the RNs at DeNB. Hence, system performance depends strongly on the resource sharing strategy among and within the links. Further, the set of subframes assigned for the relay link transmission is semi-statically configured and thus a dynamic reconfiguration to adapt to fast-changing system conditions (e.g. RN cell load) is not viable. Besides, in order to fully exploit the benefits of relaying, the inter-cell interference, which is increased because of the presence of RNs, should be limited via a proper power control (PC) scheme on each link. Therefore, an optimisation of both the resource sharing and PC strategy is required to enhance the overall performance of relay networks. In order to tackle these issues, we employ a statistic-based over-provisioned backhaul subframe allocation to be utilised for flexible co-scheduling of RNs and MUEs at the DeNB. In addition, we propose a combination of RN scheduling based on the number of RUEs and user throughput throttling achieving max-min fairness. Performance analysis of various resource sharing techniques along with PC optimisation is then carried out within the LTE-Advanced uplink framework in urban and suburban scenarios. Comprehensive results show that the proposed schemes achieve significant throughput gains and high system fairness with substantially increased flexibility in resource allocation.

End-to-End Data Rate Performance of Decode-and-Forward Relaying with Different Resource Allocation Schemes

“…In this scheme, the e2e data rate ( opt e2e ) is maximized when the same amount of data is transferred over each link at each TTI. This is equivalent to verify that opt e2e = r r = a a (11) holds for each radio frame. In order to achieve condition (11), proper resource allocation is required; that is, the selection of r , a , r , and a depends on the instantaneous SNR of each link (in principle, adjusting power is another degree of freedom; however, this work deals with infrastructure fixed relays, where the transmission power of BSs and RNs in downlink is kept constant to avoid potentially harmful cochannel interference towards the adjacent cells).…”

“…In order to achieve condition (11), proper resource allocation is required; that is, the selection of r , a , r , and a depends on the instantaneous SNR of each link (in principle, adjusting power is another degree of freedom; however, this work deals with infrastructure fixed relays, where the transmission power of BSs and RNs in downlink is kept constant to avoid potentially harmful cochannel interference towards the adjacent cells). Hence, time and bandwidth are the degrees of freedom to achieve (11). Practical implementations, such as Type 2 DF relaying in LTE-A and Mobile WiMAX [33], provide means to conveniently allocate time-frequency resources, such that optimal resourcing can be achieved or at least well approximated (due to the existence of a practical granularity in the partition of resources).…”

“…The performance and energy efficiency of relay enhanced networks have gained a lot of interest; see, for example, [5][6][7][8][9][10][11][12][13][14][15]. Recently the impact of buffer on the performance of DF relaying has also been investigated in references like [16].…”

Automated uplink power control optimization in LTE-Advanced relay networks

“…We assume that subframes configured for the relay link are assigned exclusively to RNs at the DeNB, i.e., co-scheduling of MUEs and RNs is not considered. For the resource allocation on the backhaul subframes and access link, we utilize the scheme in [28], where resource shares of the RNs on the relay link are proportional to the number of attached RUEs. The available capacity on the relay link is then distributed among RUEs utilizing max-min fairness.…”

“…The available capacity on the relay link is then distributed among RUEs utilizing max-min fairness. Moreover, the number of backhaul subframes to be allocated to RNs is chosen such that the overall system performance is optimized; two and four subframes are configured in case of urban and suburban 4-RN deployments, respectively [28].…”