A survey on 3GPP heterogeneous networks

TLDR

Cellular networks approaching spectral limits require denser deployments, yet existing dense networks suffer from severe inter‑cell interference and high macro‑node capital costs, limiting further capacity gains. The article proposes overlaying low‑power nodes within macro networks to form heterogeneous networks as an alternative to dense macro deployments. The survey reviews the 3GPP LTE air interface, node types, spectrum options, and key enabling mechanisms—such as interference management, cell‑range expansion, and interference‑cancellation receivers—for heterogeneous deployments. Cell‑range expansion via biasing and adaptive resource partitioning effectively balances load and improves trunking efficiency in heterogeneous networks.

Abstract

As the spectral efficiency of a point-to-point link in cellular networks approaches its theoretical limits, with the forecasted explosion of data traffic, there is a need for an increase in the node density to further improve network capacity. However, in already dense deployments in today's networks, cell splitting gains can be severely limited by high inter-cell interference. Moreover, high capital expenditure cost associated with high power macro nodes further limits viability of such an approach. This article discusses the need for an alternative strategy, where low power nodes are overlaid within a macro network, creating what is referred to as a heterogeneous network. We survey current state of the art in heterogeneous deployments and focus on 3GPP LTE air interface to describe future trends. A high-level overview of the 3GPP LTE air interface, network nodes, and spectrum allocation options is provided, along with the enabling mechanisms for heterogeneous deployments. Interference management techniques that are critical for LTE heterogeneous deployments are discussed in greater detail. Cell range expansion, enabled through cell biasing and adaptive resource partitioning, is seen as an effective method to balance the load among the nodes in the network and improve overall trunking efficiency. An interference cancellation receiver plays a crucial role in ensuring acquisition of weak cells and reliability of control and data reception in the presence of legacy signals.