Query to improve network performance download of large size files from sharepoint

I need suggestion on below issue:

Issue: We have a SharePoint publishing site for which we are experiencing bandwidth issues on document download. We have an 8 MB Network bandwidth allocated but when the document size is large the download consumes the whole bandwidth and hence other users experience performance issue.

Solution we tried:

1)      Tried to download from out of box download page of SharePoint

Result: No change on bandwidth consumption

2)      Created WCF service hosted in IIS sharing same application pool as my SharePoint site & stream the data(not buffer) . Following is the binding on client :

    <bindings>

      <basicHttpBinding>

        <binding name="BasicHttpBinding_IService1" closeTimeout="04:01:00" openTimeout="04:01:00" receiveTimeout="04:10:00" sendTimeout="04:01:00" allowCookies="false" bypassProxyOnLocal="false" hostNameComparisonMode="StrongWildcard" maxBufferSize="6500" maxBufferPoolSize="2147483647" maxReceivedMessageSize="2147483647" messageEncoding="Text" textEncoding="utf-8" transferMode="Streamed" useDefaultWebProxy="true">

          <readerQuotas maxDepth="128" maxStringContentLength="2147483647" maxArrayLength="2147483647" maxBytesPerRead="2147483647" maxNameTableCharCount="2147483647" />

          <security mode="None">

            <transport clientCredentialType="None" proxyCredentialType="None" realm="" />

            <message clientCredentialType="UserName" algorithmSuite="Default" />

          </security>

        </binding>

      </basicHttpBinding>

    </bindings>

    <client>

      <endpoint address="http://xyz/Service1.svc" binding="basicHttpBinding" bindingConfiguration="BasicHttpBinding_IService1" contract="ServiceReference1.IService1" name="BasicHttpBinding_IService1" />

    </client>

 We want to limit the data packet size to 4MB irrespective of file size returned from service so that individual user experience will be little slow but other user will not experience performance issues

Result: No change on bandwidth consumption