Kari Juhani Hooli

Massive carrier aggregation in LTE-advanced pro: impact on uplink control information and corresponding enhancements

3GPP began standardization of carrier aggregation (CA) in LTE-A Rel. 10 to combine up to five component carriers (CCs) for facilitating wider transmission bandwidth of 100 MHz. Further enhancements followed in Rel. 11 and Rel. 12 to enable features such as aggregation of carriers between time-division duplex (TDD) and frequency-division duplex (FDD) frame structures. In LTE-A Pro Rel. 13, massive CA enhancements were defined to combine more than five CCs with the initial focus on the downlink. While the benefits of CA have been evident, operating an even larger number of downlink carriers results in increased overhead on the uplink as there is a need to send the combined control information for all the CCs. In this article we give an overview of the standardized enhancements, their impact on uplink control information overhead and its transmission, new control channel formats and their link level investigation in 3GPP-defined simulation assumptions.

Overview of uplink control channel for carrier aggregation enhancements in LTE Rel. 13

Frequency Spectrum is a non-renewable limited radio resource and therefore every effort has been made to efficiently utilize the spectrum. In LTE Release 10, 3GPP introduced carrier aggregation as a key enabler to meet the requirements set by IMT-Advanced by combining component carriers and have an aggregated bandwidth of up to 100 MHz. Further enhancements in LTE Rel. 11 and 12 have been introduced to support several configurations in time-division duplex and frequency-division duplex. Latest developments involve expanding carrier aggregation up to 32 component carriers in LTE Rel. 13. This would have challenging implications on the current control signaling support both in the downlink and uplink. In this paper, we identify the payload for uplink control information on physical uplink control channel to support carrier aggregation enhancements, analyze the limitations of existing formats and propose a simplified yet effective solution to provide reasonable support for transmitting uplink control information with larger payload.

Fairness vs. Performance in Rel-13 LTE Licensed Assisted Access.pdf

Wireless spectrum being a valuable resource, a large number of both non-profit and for-profit users rely on its unlicensed parts, usually to provide some sort of local area wireless coverage. When the cellular vendors and service providers expressed interest in the unlicensed spectrum, the incumbent community started to fear that the new technology would not respect the existing users. And although members of the incumbent community strongly influenced the design of licensed assisted access (LAA) in 3GPP, the fear has not dispersed yet. Representing a vendor with stakes in both communities, we attempt to disperse the fear by providing insight on the question of fairness and performance of LAA, openly discussing why it should generate less interference than WiFi and why it could be otherwise. We augment the discussion with insightful simulations, looking how detailed parameters of the channel access mechanism influence LAAs fairness and performance. Our investigations show that in common scenarios LAA is a fair neighbor to WiFi as is, and even in an extreme scenario only small adjustments to the channel access mechanism are needed to achieve the same outcome.