WHY there is No-Edge Networks? what is Multi-Stream Aggregation (MSA)?

The following is from Huawei press release:


The LTE-Advanced Multi-Stream Aggregation (MSA) technology standard is capable of increasing data rates at the cell's edge. A key component of Huawei's "No-Edge Networks" concept, MSA technology coordinates macro cells to improve user data rates at the cell's edge and also between heterogeneous networking scenarios to improve peak rates and simplify mobile management to ensure a consistent user experience.

With the development of mobile broadband, operators are mostly concerned about user experience. With mobile coverage, should able to enjoy the same quality of services no matter where they are. However, with mobile communication systems, the most challenging issue is system performance at the cell's edge.

The concept behind Huawei's MSA technology is that the user is always able to receive downlink data and aggregate downlink data streams from a cell or cell group with the best signal quality. A similar method applies to uplink data, where the user always transmits uplink data to a cell or cell group with the best signal quality. The uplink data streams are aggregated on the network side.

Huawei's MSA technology reduces the number of handovers, lowering device power transmission and increasing device standby time. These advantages are in accordance with the concept of delivering a "borderless network" and "green" wireless communications. It's expected that MSA technology will improve system performance at the cell's edge by almost 30%.

MSA technology is especially suitable for macro-micro HetNets. In hotspot area, macro cells provide basic LTE coverage while the micro cells provides capacity enhancement. The use of MSA technology allows users to receive controlled signaling from macro cells and services from best quality HetNet cell. Users at any location within the network can then enjoy fast and stable data services with ultra broadband, zero waiting and ubiquitous connectivity. MSA technology brings users high speeds and high quality as well as a simple service experience.

The advanced MSA technology proposed by Huawei is set to become a key feature of the evolution to 3GPP LTE-Advanced standards. Huawei has contributed 293 core standards to the 3GPP LTE/LTE-Advanced standardization process, 20% of the global total and the most of any other company.

what is ICIC( Inter-cell interference coordination) and eICIC (enhanced Inter-cell interference coordination)

Background

• LTE is designed for frequency reuse 1 (To maximize spectrum efficiency), which means that all the neighbor cells are using same frequency channels and therefore there is no cell-planning to deal with the interference issues
• There is a high probability that a resource block scheduled to cell edge user, is also being transmitted by neighbor cell, resulting in high interference, eventually low throughput or call drops (see figure) 
• Traffic channel can sustain upto 10% of BLER in low SINR but control channels cannot. Neighbor interference can result in radio link failures at cell edge.
• Heterogeneous networks require some sort of interference mitigation, since pico-cells/femto cells and macro-cells are overlapping in many scenarios

ICIC (Inter-cell interference coordination)

• Inter-cell interference coordination is introduced in 3GPP release 8
• ICIC is introduced to deal with interference issues at cell-edge
• ICIC mitigates interference on traffic channels only
• ICIC uses power and frequency domain to mitigate cell-edge interference from neighbor cells 
• One scheme of ICIC is where neighbor eNBs use different sets of resource blocks through out the cell at given time i.e. no two neighbor eNBs will use same resource assignments for their UEs. This greatly improves cell-edge SINR. The disadvantage is decrease in throughput throughout the cell, since full resources blocks are not being utilized.
• In the second scheme, all eNBs utilize complete range of resource blocks for centrally located users but for cell-edge users, no two neighbor eNBs uses the same set of resource blocks at give time
• In the third scheme (probably the preferred scheme), all the neighbor eNBs use different power schemes across the spectrum while resource block assignment can be according to second scheme explained above. For example, eNB can use power boost for cell edge users with specific set of resources (not used by neighbors), while keeping low signal power for center users with availability of all resource blocks (see the figure)
• X2 interface is used to share the information between the eNBs

eICIC (enhanced Inter-cell interference coordination)

• eICIC introduced in 3GPP release 10
• eICIC introduced to deal interference issues in Heterogeneous Networks (HetNet)
• eICIC mitigates interference on traffic and control channels
• eICIC uses power, frequency and also time domain to mitigate intra-frequency interference in heterogeneous networks
• eICIC introduces concept of "Almost blank subframe" (ABS). ABS subframes do not send any traffic channels and are mostly control channel frames with very low power. If macro cell configure ABS subframes then UEs connected to pico/femto cells can send their data during such ABS frames and avoid interference from macro cell (see the figure)
• ABS configuration is shared via OAM or x2 interface

What is Policy charging and Rules Function (PCRF)? entity in LTE

PCRF is an important entity in the LTE core network domain, initially introduced in 3gpp rel 5. It is mainly responsible for making policy and control decisions. In simple words, if a user needs better quality of service (lets suppose in case of VoLTE ) then it is the responsibility of PCRF to initiate QoS with instructions from IMS. The functionality is listed below

• Provide QoS information to packet gateway 
• Dynamically manage and control data sessions. Example: For VoIP session, PCRF will initiate dedicated bearer dynamically
• Enforce minimum QoS parameters
• Determine charging policy for packets