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  • wimax project multiple modem MIMO

    hello, new to the forum but long time lurker. I own a small but growing marina in so California and to my dismay there are no cable providers or isps that cover my area. (the coverage ends 1500 meters away and the charge to bring it to me is huge) so to get back to the subject I have decided to use sprint to help me provide wifi to the customers at my marina through the use of appx. 6 franklin u600 usb modems and 2 cradlepoint mbr 1200
    expected bandwidth required is between 50mbps to 60 mbps. I am currently sporting a mbr 1200 with one u600 and one 18dBi panel antenna and am seeing average speeds 4-5 down and 1.2-1.5 up the cap per modem is 1.5 up so that is quite satisfying the router gives mne readings of

    Manufacturer: Franklin Wireless Corporation
    Product: U600 - 4G
    Modem Firmware Version: 6.0.1253
    Center Frequency (kHz): 2663500
    CINR (dB): 28
    Base Station ID (BSID): 000002F80120
    Transmit Power (dBm): 16
    Calibration Status: Calibrated
    Signal Strength (%): 100
    Signal Strength (dBm): -61
    PhysicalPort USB1

    closest sprint tower is appx 5.31 miles not too much 4g coverage here but im next to positive this is my bs simply looking for help designing the best setup for this project please share all that you think is helpful

  • #2
    I have decided to use sprint to help me provide wifi to the customers at my marina through the use of appx. 6 franklin u600 usb modems and 2 cradlepoint mbr 1200
    Excellent. Smart move. Incidentally have you looked at using the Cradlepoint MBR1400 router which gives you captive portal/ walled garden features which are more amenable for a public wifi hotspot. Simply this allows you to better control who is on your network, DNS redirection pushes them to a web portal where they can for example accept terms of service and learn how to gain access or for example you could have a walled garden which might be your marina website that users can browse without requiring access (free advertisement).

    By the way this router also gives you 3x MIMO 802.11n with external antennas for added range (they claim 750ft+ but i always take wireless range claims with a grain of salt). They also support 128 concurrent users vs 64 for the MBR1200 just in case you will get that high (incidentally you can also create multiple SSID's so multiple WLAN networks to segregate your users).

    Here is additional info on that: http://www.rfwel.com/downloads/datas..._Datasheet.pdf. Just a thought ...


    expected bandwidth required is between 50mbps to 60 mbps
    Seems a little high for 6 modems. Maximum sustained throughput i have seen is around the ~5mbps range so you are really on the higher side - just keep praying they don't add users without improving capacity.

    CINR (dB): 28
    Transmit Power (dBm): 16
    Signal Strength (%): 100
    Signal Strength (dBm): -61
    Your signal looks very good. Depending on how strong your Received Signal Strength (RSS) is without the 18dBi panel adding a second MIMO antenna might only marginally improve your throughputs. Honestly though i suspect you might be peaking the assigned rates and may not get much improvement unless of course you have the U600 in an RF-shielded building/enclosure which means the MIMO diversity AUX antenna is hardly receiving any signal. It never hurts to test it out either way.

    closest sprint tower is appx 5.31 miles not too much 4g coverage here but im next to positive this is my bs simply looking for help designing the best setup for this project please share all that you think is helpful
    Believe me you have quite good signal strength compared to other markets that supposedly have more dense coverage. It appears that you might not have as big a user base as other places which might be why your CINR is so good.

    Not sure if you have seen this article on MIMO antenna selection: http://www.rfwel.com/forums/content....s-Two-Antennas

    Here is another one on MIMO antenna orientation: http://www.rfwel.com/forums/content....-MIMO-Antennas

    Not much additional advice i can provide - you are clearly on the right track with this. One thing though is if you do get an 18dBi panel antenna for each modem be careful with the orientation to prevent antennas pointing at each other (which will increase noise floor and degrade CINR). You can take advantage of the relatively high 30dB front-to-back ratio of these panel antennas so for example you could put one behind the other and probably stagger them both in azimuth and elevation (azimuthal staggering might be hard to achieve if you want to use the same mast especially since you have the one BTS that you need to target) but elevation (vertical) staggering should be relatively simple.
    Last edited by Petro5; 08-18-2011, 08:39 PM.

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    • #3
      Thank you for the advice, I will definately be switching routers I was under the impression that both routers had the same capibilities excpet the wifi antenna (for future refrence and to all others viewing this thread definately recommend mbr1400 even just for the simplicity and reliability of the wifi antenna connections, mbr 1200 comes with tiny mc connections that do not stay well and the adapters are hard to find)

      had a few other things that I am debating with

      1. I am uncertian if aquiring a static ip from sprint for each modem is worth wile to be honset this is my first large network design and I have not experimented too much wilth static ip.

      2. The router will be indoors where the signial is not strong at all in most places I recieve nothing but one bar on evo 4g. I do believe that the aux antennas are starving for any signal and therefore I like the mimo idea, but per all the literature I have read and the articles you have recommended I see that for in my situation where I have a near line of site of the BTS an secondary omnidirectional antenna would be best, it is just designing a configuration for 12 total antennas is a little overwhelming for the space privided. Two masts with three antenna each is reasonable but I cannot figure how to place an additional 6 omnidirectional antenna

      3. The final bit of information that I am lacking is reasonably priced software or hardware; any type of tools to aquire more information about my signal so that I can properly place and orient my antenna

      again thank you for your imput

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      • #4
        1. I am uncertian if aquiring a static ip from sprint for each modem is worth wile to be honset this is my first large network design and I have not experimented too much wilth static ip.
        I would play first with dynamic DNS services and see how that works out for you before you commit resources to getting a Static IP address.

        2. The router will be indoors where the signial is not strong at all in most places I recieve nothing but one bar on evo 4g. I do believe that the aux antennas are starving for any signal and therefore I like the mimo idea, but per all the literature I have read and the articles you have recommended I see that for in my situation where I have a near line of site of the BTS an secondary omnidirectional antenna would be best, it is just designing a configuration for 12 total antennas is a little overwhelming for the space privided. Two masts with three antenna each is reasonable but I cannot figure how to place an additional 6 omnidirectional antenna
        While more antennas means more business for our sales dept ... under full disclosure I'm obliged to clarify that if you in fact have a very strong line-of-sight primary signal the benefit of MIMO spatial diversity is not as significant. You do of course get MIMO coding diversity gain. Spatial diversity simply means taking advantage of the spatial domain (space) for redundancy/diversity and this requires that the signal follow different paths (typically so for a multipath fading channel with reflections etc which is not so when you have a very strong line-of-sight beam). Since even in this case you do get secondary signals arriving at different angles you do get some MIMO coding advantage (different error correction codes applied to aux channel which affects your overall bit-error-rate).

        So the bottom line is i would first experiment with probably two modems and see what additional benefit the secondary antenna provides to them vs the modems without secondary outdoor antennas. It is true as you say that if the indoor modem is significantly RF-shielded as not to have any signal on the AUX port that an outdoor secondary antenna would very likely show much better performance.

        My last point on this is if the purpose of the secondary antenna is simply to overcome the RF-shielding effect of the building (and so route a decently strong signal to the AUX) then you need not use a high gain Omni antenna such as the 12dBi wimax omni antenna which is 45" long. Instead you might get comparable performance with a low-gain but lower profile 8.5dBi omni antenna which is 20" long.

        3. The final bit of information that I am lacking is reasonably priced software or hardware; any type of tools to aquire more information about my signal so that I can properly place and orient my antenna
        Your best tool is in fact the modem itself (the diagnostic pages in the communication software and the RSSI - Received Signal Strength Indicator - that is integrated into the modem). Otherwise you would need to purchase/rent a spectrum analyzer and/or protocol analyzers which for 2-3GHz operation is quite pricey!
        KF7RCQ

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        • #5
          Primarily thank you for you're speedy and honest response you have answered all questions that I had with the set up. I believe my next step will be to order the equipment I will require to add the second primary antenna for the second modem as well as a secondary small antenna so that I can measure the difference between the two modems and decide if the juice is worth the squeeze. Again I appreciate the advice especially the bit about the modem diagnostic communications pages and the info i can find there, previously I was relying on the info provided by the router.

          again thank you for your input and i think i will be updating this thread as the project moves along anyone else done something like this??

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