I have been a bit lost with all the unlicensed spectrum related terms and abbreviations listed in the title of this blog post. This post is an attempt to bring some clarity to myself and hopefully also to others who might discover the post.
Many of the technologies in the title like LTE-U, LAA, MulteFire and LWA are the result of recent developments within various standardization bodies and the telecommunications industry around data offloading to unlicensed spectrum.
LAA (Licensed Assisted Access) uses carrier aggregation in the downlink to combine LTE (Long Term Evolution) in unlicensed spectrum (5GHz, which is also used by 802.11a Wi-Fi) with LTE in the licensed band [QC-3, TVT]. The benefit of doing so is a fatter data pipe with faster data rates and more responsive user experience. LAA maintains a persistent anchor in the licensed spectrum. All control signaling information is carried in the licensed band, which ensures seamless and reliable user experience. LAA is for mobile operator deployments in Europe and Japan.
LTE-U (LTE in Unlicensed Spectrum) is the US (and Korean and Indian) version of LAA [4GA, QC-2]. It differs from LAA mostly in the way it handles contention. Whereas LAA has been specified in 3GPP, LTE-U has been defined in LTE-U Forum. LTE-U focuses on deployment options and regions where LBT (Listen Before Talk) policy, which is used by LAA, is not required. Both LTE-U and LAA dynamically select the unused channel with the least interference, avoiding Wi-Fi. At low traffic loads, they turn off transmission in the unlicensed spectrum, relying solely on the anchor of the licensed spectrum. In cases where there is no clear unused channel, they aim for fair and efficient coexistence with Wi-Fi. For this, LAA uses LBT to sense channel availability and adjust on/off LTE cycling (LTE on/off cycling is used to share the channel fairly with Wi-Fi). In contrast, LTE-U uses CSAT (Carrier-Sensing Adaptive Transmission) to sense other users and adjust on/off LTE cycling. CSAT and LBT represent fundamentally different approaches to access the channel [IEEE]. There are opinions that LTE-U/LAA are an attempt by mobile network operators to expand into the Wi-Fi spectrum and push out the Wi-Fi operators [TVT].
MulteFire is an LTE-based technology that, unlike LAA and LTE-U, solely operates in unlicensed spectrum without requiring an anchor in licensed spectrum [QC-1]. It broadens the LTE ecosystem to entities that may not own licensed spectrum, including ISPs (Internet Service Providers) and enterprise and venue owners. MulteFire is claimed to combine the performance benefits of LTE technology such as enhanced capacity, range, mobility and quality of experience with the simplicity of Wi-Fi like deployments. MulteFire is suitable for neutral host services. Neutral host is an LTE deployment that can be used by subscribers irrespective of their service provider. In the neutral host model, any deployment (e.g., by an ISP or enterprise or venue owner) can provide wireless access services to any end user without requiring a SIM or subscription, using neutral unlicensed spectrum. MulteFire can also interface with mobile networks to offer data offload services to mobile operators. Finally, MulteFire can be used to create private LTE networks using unlicensed spectrum bands [QC-4] for example for Industrial Internet of Things (IIoT) or enterprise use.
LWA (LTE Wi-Fi Aggregation) differs from LAA and LTE-U since LWA access in the unlicensed spectrum is based on IEEE 802.11 (i.e., Wi-Fi) standards [NOK]. LWA uses both LTE and WLAN (Wireless Local Area Network) interfaces in parallel: LTE provides reliable connectivity and mobility and Wi-Fi boosts data capacity and improves coverage. LWA aggregates data at the radio access network where Evolved NodeB (eNB; a base station) schedules packets to be served on LTE and Wi-Fi radio links [4GA]. LWA supports downlink aggregation at the PDCP (Packet Data Convergence Protocol; one of the user plane protocols in LTE that sends and receives packets to and from User Equipment (UE) and eNodeB over air interface) layer. It supports uplink transmissions only on the LTE network. LWA introduces a new direct interface Xw, which is defined between LTE and Wi-Fi. The Xw interface is terminated at the WT (WLAN termination), which is a new 3GPP logical node that may be in control of one or more WLAN APs (Access Points).
QUIC (Quick User Datagram Protocol Internet Connections) and Multipath TCP (Transmission Control Protocol) are options for multi-connectivity/aggregation that occur at the network level [4GA]. They can work with any combination of licensed and unlicensed band technologies, including future ones such as 5G. QUIC is a transport protocol that supports a set of multiplexed connections between two endpoints over UDP (User Datagram Protocol). It provides security equivalent to TLS/SSL (Transport Layer Security and Secure Sockets Layer) together with reduced connection and transport latency, and bandwidth estimation in each direction to avoid congestion [WP]. IETF’s (Internet Engineering Task Force) QUIC Working Group (WG) is looking into extending QUIC’s core protocol facilities to enable multipath capabilities for connection migration between paths and load sharing across multiple paths [IETF]. This would also enable the parallel use of Wi-Fi and LTE interfaces to download content. Multipath TCP is another ongoing effort in the IETF that aims at allowing a TCP connection to use multiple paths to maximize resource usage and increase redundancy [WP-2]. The use of both Wi-Fi and a mobile network is a typical use case for Multipath TCP. Multipath TCP can split data and transmit them through both LTE and Wi-Fi networks in parallel. LTE-Wi-Fi aggregation takes place between a device and MPTCP proxy, meaning that no dedicated network equipment is required for aggregation additionally [NM].
There exists a bunch of other exciting unlicensed spectrum related abbreviations and technologies that I plan to look into in a future blog post, including CBRS, LAS, SAS, PAL, GAA, and ESC. Stay tuned!
Although this blog post focused on LTE in unlicensed spectrum, unlicensed spectrum will also be key in boosting data rates in 5G NR (5G New Radio), which is the topic of another blog post.
(If I counted right, I managed to fit over 30 different abbreviations into this blog post).
[4GA] LTE Aggregation & Unlicensed Spectrum, http://www.4gamericas.org/files/1214/4648/2397/4G_Americas_LTE_Aggregation__Unlicensed_Spectrum_White_Paper_-_November_2015.pdf
[IEEE] Unlicensed LTE/WiFi coexistence: Is LBT inherently fairer than CSAT?, http://ieeexplore.ieee.org/document/7510910/
[IETF] IETF’s QUIC Working Group Charter, https://datatracker.ietf.org/wg/quic/charter/
[MG] Google’s QUIC protocol: moving the web from TCP to UDP, https://ma.ttias.be/googles-quic-protocol-moving-web-tcp-udp/
[NM] Analysis of LTE – WiFi Aggregation Solutions, http://www.netmanias.com/en/post/reports/8532/laa-lte-lte-u-lwa-mptcp-wi-fi/analysis-of-lte-wifi-aggregation-solutions
[NOK] Unlicensed band opportunities for mobile broadband, http://resources.alcatel-lucent.com/asset/200296
[QC-1] Introducing MulteFire: LTE-like performance with Wi-Fi-like simplicity, https://www.qualcomm.com/news/onq/2015/06/11/introducing-multefire-lte-performance-wi-fi-simplicity
[QC-2] How different are LTE-U and LAA?, https://www.qualcomm.com/news/onq/2015/11/04/how-different-are-lte-u-and-laa
[QC-3] Extending LTE to unlicensed spectrum globally – LAA, https://www.qualcomm.com/invention/technologies/lte/laa
[QC-4] GE, Nokia and Qualcomm Unveil First Private LTE-based Trial Network Customized for Industrial IoT, https://www.qualcomm.com/news/releases/2017/02/22/ge-nokia-and-qualcomm-unveil-first-private-lte-based-trial-network
[TVT] LWA offers aggregation without the aggravation: the alternative acronym to LTE-U and LAA, http://www.telecomtv.com/articles/wi-fi/lwa-offers-aggregation-without-the-aggravation-the-alternative-acronym-to-lte-u-and-laa-12804/
[WP] QUIC, https://en.wikipedia.org/wiki/QUIC
[WP-2] Multipath TCP, https://en.wikipedia.org/wiki/Multipath_TCP
Many of the technologies in the title like LTE-U, LAA, MulteFire and LWA are the result of recent developments within various standardization bodies and the telecommunications industry around data offloading to unlicensed spectrum.
LAA (Licensed Assisted Access) uses carrier aggregation in the downlink to combine LTE (Long Term Evolution) in unlicensed spectrum (5GHz, which is also used by 802.11a Wi-Fi) with LTE in the licensed band [QC-3, TVT]. The benefit of doing so is a fatter data pipe with faster data rates and more responsive user experience. LAA maintains a persistent anchor in the licensed spectrum. All control signaling information is carried in the licensed band, which ensures seamless and reliable user experience. LAA is for mobile operator deployments in Europe and Japan.
LTE-U (LTE in Unlicensed Spectrum) is the US (and Korean and Indian) version of LAA [4GA, QC-2]. It differs from LAA mostly in the way it handles contention. Whereas LAA has been specified in 3GPP, LTE-U has been defined in LTE-U Forum. LTE-U focuses on deployment options and regions where LBT (Listen Before Talk) policy, which is used by LAA, is not required. Both LTE-U and LAA dynamically select the unused channel with the least interference, avoiding Wi-Fi. At low traffic loads, they turn off transmission in the unlicensed spectrum, relying solely on the anchor of the licensed spectrum. In cases where there is no clear unused channel, they aim for fair and efficient coexistence with Wi-Fi. For this, LAA uses LBT to sense channel availability and adjust on/off LTE cycling (LTE on/off cycling is used to share the channel fairly with Wi-Fi). In contrast, LTE-U uses CSAT (Carrier-Sensing Adaptive Transmission) to sense other users and adjust on/off LTE cycling. CSAT and LBT represent fundamentally different approaches to access the channel [IEEE]. There are opinions that LTE-U/LAA are an attempt by mobile network operators to expand into the Wi-Fi spectrum and push out the Wi-Fi operators [TVT].
MulteFire is an LTE-based technology that, unlike LAA and LTE-U, solely operates in unlicensed spectrum without requiring an anchor in licensed spectrum [QC-1]. It broadens the LTE ecosystem to entities that may not own licensed spectrum, including ISPs (Internet Service Providers) and enterprise and venue owners. MulteFire is claimed to combine the performance benefits of LTE technology such as enhanced capacity, range, mobility and quality of experience with the simplicity of Wi-Fi like deployments. MulteFire is suitable for neutral host services. Neutral host is an LTE deployment that can be used by subscribers irrespective of their service provider. In the neutral host model, any deployment (e.g., by an ISP or enterprise or venue owner) can provide wireless access services to any end user without requiring a SIM or subscription, using neutral unlicensed spectrum. MulteFire can also interface with mobile networks to offer data offload services to mobile operators. Finally, MulteFire can be used to create private LTE networks using unlicensed spectrum bands [QC-4] for example for Industrial Internet of Things (IIoT) or enterprise use.
LWA (LTE Wi-Fi Aggregation) differs from LAA and LTE-U since LWA access in the unlicensed spectrum is based on IEEE 802.11 (i.e., Wi-Fi) standards [NOK]. LWA uses both LTE and WLAN (Wireless Local Area Network) interfaces in parallel: LTE provides reliable connectivity and mobility and Wi-Fi boosts data capacity and improves coverage. LWA aggregates data at the radio access network where Evolved NodeB (eNB; a base station) schedules packets to be served on LTE and Wi-Fi radio links [4GA]. LWA supports downlink aggregation at the PDCP (Packet Data Convergence Protocol; one of the user plane protocols in LTE that sends and receives packets to and from User Equipment (UE) and eNodeB over air interface) layer. It supports uplink transmissions only on the LTE network. LWA introduces a new direct interface Xw, which is defined between LTE and Wi-Fi. The Xw interface is terminated at the WT (WLAN termination), which is a new 3GPP logical node that may be in control of one or more WLAN APs (Access Points).
QUIC (Quick User Datagram Protocol Internet Connections) and Multipath TCP (Transmission Control Protocol) are options for multi-connectivity/aggregation that occur at the network level [4GA]. They can work with any combination of licensed and unlicensed band technologies, including future ones such as 5G. QUIC is a transport protocol that supports a set of multiplexed connections between two endpoints over UDP (User Datagram Protocol). It provides security equivalent to TLS/SSL (Transport Layer Security and Secure Sockets Layer) together with reduced connection and transport latency, and bandwidth estimation in each direction to avoid congestion [WP]. IETF’s (Internet Engineering Task Force) QUIC Working Group (WG) is looking into extending QUIC’s core protocol facilities to enable multipath capabilities for connection migration between paths and load sharing across multiple paths [IETF]. This would also enable the parallel use of Wi-Fi and LTE interfaces to download content. Multipath TCP is another ongoing effort in the IETF that aims at allowing a TCP connection to use multiple paths to maximize resource usage and increase redundancy [WP-2]. The use of both Wi-Fi and a mobile network is a typical use case for Multipath TCP. Multipath TCP can split data and transmit them through both LTE and Wi-Fi networks in parallel. LTE-Wi-Fi aggregation takes place between a device and MPTCP proxy, meaning that no dedicated network equipment is required for aggregation additionally [NM].
There exists a bunch of other exciting unlicensed spectrum related abbreviations and technologies that I plan to look into in a future blog post, including CBRS, LAS, SAS, PAL, GAA, and ESC. Stay tuned!
Although this blog post focused on LTE in unlicensed spectrum, unlicensed spectrum will also be key in boosting data rates in 5G NR (5G New Radio), which is the topic of another blog post.
(If I counted right, I managed to fit over 30 different abbreviations into this blog post).
References
[4GA] LTE Aggregation & Unlicensed Spectrum, http://www.4gamericas.org/files/1214/4648/2397/4G_Americas_LTE_Aggregation__Unlicensed_Spectrum_White_Paper_-_November_2015.pdf
[IEEE] Unlicensed LTE/WiFi coexistence: Is LBT inherently fairer than CSAT?, http://ieeexplore.ieee.org/document/7510910/
[IETF] IETF’s QUIC Working Group Charter, https://datatracker.ietf.org/wg/quic/charter/
[MG] Google’s QUIC protocol: moving the web from TCP to UDP, https://ma.ttias.be/googles-quic-protocol-moving-web-tcp-udp/
[NM] Analysis of LTE – WiFi Aggregation Solutions, http://www.netmanias.com/en/post/reports/8532/laa-lte-lte-u-lwa-mptcp-wi-fi/analysis-of-lte-wifi-aggregation-solutions
[NOK] Unlicensed band opportunities for mobile broadband, http://resources.alcatel-lucent.com/asset/200296
[QC-1] Introducing MulteFire: LTE-like performance with Wi-Fi-like simplicity, https://www.qualcomm.com/news/onq/2015/06/11/introducing-multefire-lte-performance-wi-fi-simplicity
[QC-2] How different are LTE-U and LAA?, https://www.qualcomm.com/news/onq/2015/11/04/how-different-are-lte-u-and-laa
[QC-3] Extending LTE to unlicensed spectrum globally – LAA, https://www.qualcomm.com/invention/technologies/lte/laa
[QC-4] GE, Nokia and Qualcomm Unveil First Private LTE-based Trial Network Customized for Industrial IoT, https://www.qualcomm.com/news/releases/2017/02/22/ge-nokia-and-qualcomm-unveil-first-private-lte-based-trial-network
[TVT] LWA offers aggregation without the aggravation: the alternative acronym to LTE-U and LAA, http://www.telecomtv.com/articles/wi-fi/lwa-offers-aggregation-without-the-aggravation-the-alternative-acronym-to-lte-u-and-laa-12804/
[WP] QUIC, https://en.wikipedia.org/wiki/QUIC
[WP-2] Multipath TCP, https://en.wikipedia.org/wiki/Multipath_TCP
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