6 ms·

4G definitions are still largely being fought over, and you're gonna try and jam "5G" down my throat? The entire article is complete speculation, and the sad p

• xorlord 11y ago
  >They're trying to come up with sub specifications to encompass more types of network use cases rather than thinking "xG is for cellular phones" it'll be more like 5Gx is spectrum/protocol for home internet, 5Gy is the spectrum/protocol the phone uses. Although from a marketing prospective this will sound like "Bring 5G to your home." Intermingling the data and transport layers initially strikes me as a bad thing. What am I missing?
  • kalleboo 11y ago
    I imagine supporting signaling in motion and with limited battery and heat budget has a very different profile than at a fixed point with task-specific hardware.
  • jerf 11y ago
    That the data and transport layers are almost always intermingled, because the "OSI network model" you were taught about in school is basically a lie. (At least inasmuch as it is claimed to describe anything in the real world. As a source of vocabulary, it's at least OK, though it does suffer from people using numbers where I would rather they used the names of the layers. Much like RAID terminology is still impenetrable to me despite the several dozen times I've read the definitions.)
    • mafribe 11y ago
      data and transport layers are almost always intermingled In what sense other than NATing, which has been a stop-gap measure to deal with IPv4 address shortage? TCP/UDP sit on top of the network layer, not the data (link) layer. And the two main requirements that TCP/UDP make of the network layer is (1) that all network layer connected devices (interfaces) have a unique address and (2) you can send packets between any two network connected devices (interfaces) in a best-effort way. What the transport layer adds on top of that is - multiplexing of network layer addresses (TCP and UDP use port numbers for this) so multiple processes can share a single network layer connection and - error detection/correction (TCP only) to transform the unreliable (best effort) service the network layer offers into a reliable service. - Streaming (TCP only): the sender's data stream that a TCP client creates is split into packets and later reassembled. I think it's a beautiful separation of concerns.
      • jerf 11y ago
        That's still the beautiful model you're referencing, not the reality of networking. If you saw what the actual network devices in the stack were doing, you would be... less impressed by the beauty, let's say. But they work, and they're fast. That has beauty of its own. And I mean real network hardware through which the packets your received these words are, too, not just abstract theoretical "somebody's got something somewhere that does something weird". The model hasn't been accurate since before it was created.
        • mafribe 11y ago
• f00fc0d3 11y ago
  This is totally wishful thinking. No one in industry has a slightest idea what 5G will be. We keep throwing fancy terms like eNodeB virtualization and then we have a reality check - LTE userplane cannot be virtualized due latency and performance reasons (LTE PHY on x86 - yeah, right...). Same goes to those mm waves with beamforming - no DSP (IP core) can handle it now and even soon. You need to stick with very expensive FPGAs. Besides that there is WiGig coming and you can offload traffic from LTE to Wifi - investing in those mm wave small cells seems rather pointless. Beside that you can get those multi-Gbps with new Rel13 LTE carrier aggregation (up 32 CC).
  • the_mitsuhiko 11y ago
    > LTE userplane cannot be virtualized due latency and performance reasons Care to elaborate? I fail to see what the technical challenges are. Many services are already virtualized just on different layers if I understand this correctly (for instance Wifi calling).
    • f00fc0d3 11y ago
      HARQ loop in LTE is tight = 3 ms(3ms for ENB, 3ms for UE, 2 ms for air/RRH = 8 ms in total). It means that in those 3 ms you need to decode ack nacks in PHY, run scheduling and then send the data on other side of PHY. LTE PHY requires a lot of algorithms that doesn't fit well on x86 or general purpose HW like FFT or turbo decoding. Those usually are done in HW accelerators of baseband SOCs. x86 lacks also complex arithmetic ISA, where wireless DSP do many complex multiplies in on cycle and complex ops are ~80% of signal processing done on DSP (not accelerators). Second things is energy consumption, take e.g. Ceva XC4500 DSP core and a equivalent Xeon - it is magnitudes more efficient. In case of FFT or turbo it gets even worse. Lastly, IQ data streams requires a lot of bandwidth ~1Gbps per one carrier in case of 20MHz. FDD LTE uses mostly 2 or 4 antennas in each direction, where TDD is good with 8 antennas, and this just one cell(sector). Newest ENB can handle up to 96 cells (with 2 antennas) in one box. In theory you could run non-PHY layers of uplane in a server and use ENB as a L1 server, but still the lower MAC and scheduler needs tight latencies so server with DPDK is a must, but ARM/PowerPC/MIPS parts of the basebands SoCs are left idle (not really useful for PHY). PDCP layer seems reasonable to run in SDN because of carrier aggregation and not so tight latency requirements, but this layer is very simple. Of course you can run whole control plane in a cloud, which actually makes sense but this is not a great achievement ;-)
• the_mitsuhiko 11y ago
  > 4G definitions are still largely being fought over In which world (other than T-Mobile US) does 4G mean anything other than LTE Advanced? Sure, there was a fight for many years but it was because of carrier marketing, not because of real technical grounds. At least on a basic level I am quite interested in what comes out of the 5G efforts because what's being discussed will be very interesting for new use cases that cannot be done on existing networks.